O2 Ireland, the State's second biggest mobile network, added 43,000 new customers in the three months leading up to Christmas.
The majority of the new customers - some 40,000 - are using pre-pay handsets, suggesting strong holiday season sales for O2.
The firm's third-quarter results also show its customers spend significantly more on mobile calls than other MMO2 group subsidiaries.
Mirroring similarly strong results released by Vodafone Ireland last week, O2 Ireland said its customers spent an average of €516 per year on mobile services.
This means O2 Ireland subscribers spend €148 more than subscribers to O2 UK, €195 more than subscribers to O2 Germany and €254 more than subscribers to O2's Dutch subsidiary.
Ms Danuta Gray, chief executive of O2 Ireland, said the high average revenue per user figures were generated because Irish people use their mobiles more.
She said the high revenue figures did not mean O2 Ireland charged more than other MMO2 subsidiaries. In fact, surveys had found mobile charges here were cheaper than in other countries.
But O2 Ireland - in a similar fashion to Vodafone Ireland last week - did not publish data on the average number of minutes that Irish people use their mobiles.
This makes it impossible for viable comparisons between the different MMO2 group companies.
Ms Gray said it was group policy not to disclose the figures.
She said she was happy with O2 Ireland's strong performance and interest that had been generated in multimedia messaging in the three months to the end of December 2002. The market for multimedia phones should reach 10 per cent within 18 months, said Ms Gray.
The key performance figures show O2 Ireland subscribers sent 259 million text messages in the quarter. But in contrast to the latest Vodafone results, mobile data accounted for just 15.7 per cent of service revenues. This was the lowest performance in this key area for all MMO2 group firms.
Meanwhile, O2 Ireland's parent, the British mobile phone group MMO2, beat its forecasts by adding 791,000 customers.
It also confirmed it was in talks about selling its loss-making Dutch mobile phone business.
But MMO2 shares fell 3.6 per cent in early trading when it said that it was extended a German network-sharing deal. Analysts are worried that Europe's fifth-largest mobile operator had deepened its commitment to Germany, despite strong competition in that market.
