Google Inc. reported today that paid clicks in the first three months of this year increased 18% from the first quarter of 2010, and 4% from the fourth quarter of 2010.

In reporting its first quarter results today, Google said average cost per click increased approximately 8% year over year and 1% from the fourth quarter of 2010.

Google reported revenue of $8.58 billion in the first quarter ending March 31, up 26.7% from first quarter 2010 revenue of $6.77 billion. Net income rose 17.3% to $2.30 billion, up from $1.96 billion a year ago.

Google-owned sites accounted for $5.88 billion, or 68.5% of revenue in the first quarter, compared with $4.44 billion for the same period last year. Ads Google places on others’ web sites through its AdSense program accounted for $2.43 billion, or 28.3% of total revenue during the quarter, and is up 19.1% year over year.

Revenue generated from outside of the United States totaled $4.57 billion, representing 53.3% of total revenue in the first quarter of 2011.

“We had a great quarter with 27% year-over-year revenue growth,” says Patrick Pichette, Google’s chief financial officer. “These results demonstrate the value of search and search ads to our users and customers, as well as the extraordinary potential of areas like display and mobile. It’s clear that our past investments have been crucial to our success today—which is why we continue to invest for the long term.”