When it comes to finding a good plumber, painter or handyman, a lot of people turn to online review sites.

Consumer Reports looked at several to see how they work and how accurate they may be.

Dr. Judy Weisman wanted to hire a house cleaner, so she registered with Angie's List. Like other ratings services, Angie's List says its grades are based on reviews from real customers.

"Angie's List rated this business with an A," Weisman said. "But I had to go behind them after they had left and dust areas that were supposed to have been cleaned. I would have given it no better than a B."

Consumer Reports says it's not unusual to disagree with a review, but be wary of jumping on companies at the top of a search.

"We've found that businesses with A or B ratings who also pay for advertising, rise to the top of the default search results on Angie's List. It's a big advantage," said Consumer Reports' Margot Gilman.

Consumer Reports checked out other websites including Yelp and Google Plus Local.

"Yelp also allows businesses to buy their way to the top of default search results," Gilman said. "But, unlike Angie's List, Yelp clearly labels ads."

Bottom line, Consumer Reports said ratings services are not perfect.  They found ratings for the same business could vary a lot from site to site.

"I think there's really no substitute for using family and friends for references," Weisman said.

However, if you cant get a recommendation from someone you know, Consumer Reports says it may be worth looking up a business on several online ratings sites.