This was a 56% increase on the figure for the corresponding period in 2003 and was driven by an 11% increase in its customer base and higher revenues from existing customers.
O2 said its customer base has risen to 1.39 million, with strong growth in the January to March period normally a quiet time for mobile phone companies following the Christmas rush.
C hief executive Danuta Grey said the increase in its subscriber base and the amount of time users spend on their mobiles pushed up full-year revenues from E645m to E720m.
Ms Gray said yesterday: "For a market reaching saturation ... we had a strong set of results."
Figures released by O2 showed Irish customers spent on average of E559 on their mobile phone.
The average revenue-per-user (ARPU) for pre-paid customers was E357, while ARPU for contract customers was E1,061.
But Ms Gray said that customers in Ireland were getting good value by using their phones more and that prices had come down by 6% over the past year and would were continuing to decrease following a 16% cut price cut last November.
She added Irish people tend to use their mobile phone more than most other European countries. O2 customers in Britain use their phones for 123 minutes per month, Germans for 118 per and Irish customers for 197 minutes every month.
The operator, which has a 40% market share, said 1,194 million text messages were sent in the 12 months to end March 2004, up from 992 million the previous year. Around 340 million text message were sent between January and March alone.
Revenues from text messages and other data services, such as picture messaging, now accounted for 20% of the total revenue, a 4.7% increase.
O2 said the roll-out of third generation mobile phones, which offer better games and faster internet services would begin later this year and the company was spending 3m a week building up its network.
The company said it was also looking at ensuring that pornographic pictures would not be sent over camera phones. The operating said it's is looking at ways to ensure that anyone under the age of 18 does not receive or view obscene content.
It was looking to develop technology to filter out these type of pictures. However, O2 said it may also offer premium adult content over its next generation of mobile phones to anyone over 18.