For the dedicated, skateboarding is an art form, a proper sport. For others, it's just a teenage trend. For their parents, it's a costly and sometimes  hazardous hobby. For the casual observer, it's a nuisance, teenagers desecrating and dominating public spaces. Sue Carter gets to grips with a subculture

They descend on the plaza by the Cork Opera House on Saturday afternoons. There are always about 100 of them, even more some days, jumping, bumping, shouting and whooping. Their arrival instantly irritates city strollers and outdoor diners at the restaurant overlooking the square, Luigi Malone's. They set up their mini-ramps and the games begin.

Restaurant staff at Luigi Malone's regard them as little pests; too loud, too alternative-looking and their presence casts a constant shadow on what should be a peaceful plaza in Cork. Passers-by always glare, shaking their heads in a display of disgust. The teenagers don't care. They're here to skateboard.

The Saturday afternoon crowd, just like the sport, is male-dominated. Ugly bruises, broken bones and male competitiveness keep the girls on the sideline looking on. Some come to learn to skate, but mostly end up just hanging out.

Amy O'Leary and Linda Egerton, who are both 14 years old and both from Douglas in Cork, hang around outside the Opera House every Saturday. Amy is learning how to skateboard - "well she's trying anyway," jokes Owen Kelleher (14) from Togher, who developed an interest in the sport last summer. Amy's skills seem limited to lying on the ground as a prop while the guys demonstrate their tricks by jumping over her.

"Skateboarders are a friendly bunch, if you want to learn how to do it, you just come here and ask people to show you," says Kelleher, who's showing off his skills, doing kick-flips and kaspers - one of the many variations on a jump.

Surfer beads, chains, bracelet spikes and piercings decorate the skaters.

Some of the kids have five or six earrings, but it's pierced belly-buttons, eyebrows and nipples that give you street cred. That's what separates the skaters from the wannabes.

The vibes of hip-hop, rap and new metal are what get the skateboarders moving. Marilyn Manson, Blink, Tupac and Limp Bizkit are favourites, but the teenagers seem to like anything alternative and non-mainstream.

"We go for the underground scene when it comes to music," says Noelle Lynch (14).

It's easy to look the part: Baggy trousers, hoodies, baseball caps and professional skateboarding runners. It's a ubiquitous, unisex fashion. The tracksuit couture is trendy with all teens, not just with skateboarders. But labels matter in this subculture.

Specialist skate shops supplying the hip labels have seen their customer base rapidly expand in the past year as skateboarding has re-emerged as a teen trend.

Skate City in Dublin's Temple Bar and the Washington Street-based Primetime in Cork are two of the best-established stores. Selling everything from skateboards to fashion tops, these dedicated shops are the nucleus of teen skate culture. Skateboarding videos, hip labels and, most importantly, the professional shoes are the accessories that every teen craves.

Skateboarding fashions vary. Some favour the Californian-baseball look, while others adopt a new-metal punk image, but all skaters wear the professional runners, which are an integral part of the sport. And it is all about the sport. You can dress the part, but you can't fake the moves.

Hanging around is fun, everyone knows everyone else, but peer admiration is what all skateboarders seek, says Eoin Ryan (15) from Montenotte.

The teenagers spend hours practising jumps and tricks, but are limited in the spaces that are available to them. There is a special skateboard park in Cork city where all the older and more professional guys go, but the expense of it keeps the younger teenagers on the streets.

"It's €20 for two hours in the park - I couldn't afford to pay that every week. As it is, I travel by bus from Bandon every Saturday to skateboard here," says Steven Fitzgerald.

His parents complain about the amount of money he spends on it - they don't get the skateboarding thing and why he dedicates his Saturdays to it. Apparently it's a common complaint among the parents of skateboarders. The equipment is expensive: boards can cost up to €200 and break easily due to wear and tear, so it takes more than pocket-money to keep the teenagers on the streets. Parents are also conscious that the street skateboarders are seen as a nuisance.

Skateboarders in Dublin city centre say they suffer constant harassment from the authorities. They get hunted out of parks and shooed away from street corners. The Bank of Ireland Headquarters on Baggot Street in central Dublin is a mecca for skateboarders. Come early evenings when the security guards have gone home, teenagers swoop on the plaza. Some nights there's around 20 of them, other nights it's just a few lonely figures twisting and jumping. They're always on the watch for gardaí and scatter when they do, inevitably, arrive.

"We could go to Ramp'N'Rail, the skate park in Drumcondra in north Dublin, but we prefer doing this on the streets most evenings.

"The parks are used by the older and really experienced skaters, and we just want to practise moves, but it is a constant battle with the authorities," says Liam Mulligan (15) from Donnybrook, Dublin.

"It's not a battle we seek out though," says his friend, Larry Madden (16). "We'd prefer not to have to deal with the hassle we get, but you can't avoid it."

Urban architecture fascinates them. They look at buildings differently from other teenagers. Open concrete plazas are blank canvases, the paving slabs become their performance arenas. Steps are jumps, ramps mean speed and angles hold challenges.

Ramp'N'Rail in Drumcondra is run by Mike Keane, a big name on the skateboarding scene in the State.

"I've been skating for donkey's years. The dedicated skateboarders come to the park and the ones that hang around Temple Bar and Baggot Street aren't the best skaters.

"It's a sport that attracts people from all walks of life, there's no skater stereotype really and the scene is growing all the time. Skateboarding takes up all your time - it's not like football, where you may train and practise an hour a day or something. This takes up all your time because you are always practising new moves," he said.

For the dedicated, skateboarding is an art form, a sport they apply themselves too. For others, though, it's just a teenage trend. It's the image, the music and the social scene that attracts them. Like teenagers through the ages, they are driven by a desire to be different.