More than one-third of female sex workers surveyed for the report by the International Organization for Migration said they entered the sector through the sale of their virginity.
Some Asian cultures believe that sleeping with young virgins helps preserve virility and vitality.
The report said 203 women and girls working in brothels and places like nightclubs and bars were interviewed in depth for the study.
The average age of girls who sold their virginity was 16-17 years old, it said.
Though some girls sold their virginity voluntarily, many were tricked into the trade by friends and relatives or were forced by poverty and domestic violence into it, the report said.
"While in the majority of instances this trade appears to be voluntary for women and girls selling their virginity, there was a high use of force and incapacitation through drugs or alcohol at the time of commercial sex," it said.
It said 18 percent of women and girls were incapacitated in some way, with up to 10 percent being completely unconscious.
The findings indicated that Cambodian men, who accounted for 49 percent of the market for virgins, are the primary customers for commercial sex trafficking, especially the trade in virgins, the report said. Other Asian clients were Chinese, Japanese, South Koreans, Taiwanese, Thais and Filipinos, it said.
Westerners accounted for 9 percent, it said.
The study was conducted in Siam Reap and Koh Kong provinces and in the city of Sihanoukville, which are trafficking "hot spots" in northwestern and southwestern Cambodia mainly because of their links with tourism and foreign-led demand, IOM said.
Thirty-eight percent of the women and girls interviewed had their virginity sold, and they collected an average of US$482 (EUR347), the report said. In most cases middlemen pocketed sizable amounts from the deals, Brown said.
Trafficking of women and girls for sexual exploitation is widespread in Cambodia, which has weak law enforcement. In recent years, authorities have stepped up efforts to crack down on sex offenders, but have focused on Westerners who prey on children.