Optus, which is owned by SingTel, said net profit rose to $125 million in the 3 months ended September, up from $123 million in the prior corresponding period.
The result helped lift its first half profit by 1 per cent to $247 million.
"Optus is tracking in line with guidance despite competitive pressures in mobile and wireless broadband and the impact of iPhone 3G subsidies," chief executive Paul O'Sullivan said.
"These are positive results from Optus and our accelerating top-line growth in mobile reflects our focus on driving mobile performance," Mr O'Sullivan said.
"Compelling and market-changing offers like the iPhone 3G and `yes' Timeless plans contributed to growth in our subscriber base."
About 90 per cent of the Australian population is now covered by Optus 3G.
Optus added 182,000 new subscribers in the quarter - including a record 128,000 postpaid additions - bringing the total number of mobile customers to 7.4 million.
The number of 3G subscribers increased to 2.16 million.
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