Among the people who watched primetime programming both online and on a DVR, 35 percent watched four or more episodes online, compared with 15 percent for people who watched primetime programming both online and on live television.

"During the past year, there has been much debate about the perils of making television programming available via the Internet," said Amanda Welsh, head of research for Integrated Media Measurement Inc.

"While some have speculated or feared that online accessibility would cannibalize television audiences, our data shows that the affinity of DVR users to view television episodes online offers advertisers new opportunities to recapture a desirable audience that had been slipping away."

Among people who watched primetime programming both online and on a DVR, 30 percent went online only once, compared with 57 percent for people who watched primetime programming both online and on live television.

"Rather than simply cannibalizing audiences as has been feared, offering content online presents a huge opportunity for television content providers and advertisers to reach elusive ad-avoiding audiences and to achieve higher engagement with them," said Welsh.

More than twenty percent of people view some amount of primetime television online. Within the group of online viewers, 50 percent are watching programming as it becomes available and are using the computer as replacement for the television set. 

The other 50 percent are using the Internet to watch previous programs they missed, or to re-watch clips of episodes they have already seen.

The report indicated that in a number of instances, online viewing of a particular program was higher than DVR viewing of that same program. This suggests that a fair large proportion of non-DVR owners are using their PCs to watch TV online instead of buying a DVR.

The report found that the largest group of online TV viewers are white, affluent, well-educated, working women between the ages of 25 to 44. This group of women don’t have time to watch all of their shows live so they use the Internet as a way to watch shows they have missed on TV.

"This is the first study to show there are a significant amount of people watching primetime shows online who are not watching some portion of those shows on television," said Amanda Welsh, head of research for IMMI.

"Everyone’s been talking about the Internet becoming a substitute for television; however, this is the first single-source passive data to show that the migration from one platform to another is actually occurring — and it’s happening fast."