SK Telecom has turned in a 44.3% increase in net profit for 2013, while rival KT saw its profit fall 83.6% over the same period.
SK Telecom reported net income for the year of 1.61 trillion won ($1.49 billion), with revenue increasing 2.9% to 16.6 trillion won.
The company said increased LTE revenues compensated for revenue-decreasing promotional efforts including the introduction of plans with unlimited in-network voice calls.
The company's LTE subscriber base grew to 13.5 million by the end of the year, representing around 50% of its total mobile customer base. Churn meanwhile decreased by 0.3 percentage points to 2.3%
But a major contributor to the company's profit growth was the performance of non-core subsidiaries including chipmaker SK Hynix.
KT's annual profit by contrast declined to 181 billion won, on 0.2% lower revenue of 23.8 trillion won. The company blamed a 6.7% decline in fixed-line revenue for the declines.
For the fourth quarter, KT swung to a loss of 300 billion won from a net profit of 106.6 billion won in 4Q12.
But the company more than doubled its LTE subscriber base to 8 million for the year, and expects growth in the segment to help the company's mobile business gain ground in 2014.