Revenues grew 50.6% over the period, to $25.521 billion.
Rosneft said the drop in the net profit was down to a heavier tax burden, with all taxes, except for the profit tax, increased by 22.4%, and the export duty up 66.2%.
Profits before interest, taxes, depreciation and amortization (EBITDA) grew 13.6% to $6.395 year-on-year between January and September, up from $5.627 billion in the same period last year.
Net cash flow from operating activities grew to $3.56 billion in the first nine months of this year, a 79.3% increase on last year's $1.985 billion.
Capital investments increased 64.9% to $2.131 billion, from $1.292 billion a year ago.
Natural gas production grew 7.5% to 10.12 billion cubic meters in January-September 2006, up from 9.41 billion cu m in the same period last year.