Laura Ferris of the University of Pittsburgh Medical Center tested four apps using smartphone pictures of melanomas, or skin cancer.
Three of the apps made a diagnosis based on automated computer processes, while a fourth app sent the picture to a dermatologist for diagnosis, Ferris said.
The study, published in the journal Dermatology, found the three apps using automated computer processes were wrong 30 percent of the time, but the dermatologist was correct almost always.
"We're not ready to take the physician out of the picture quite yet," Ferris said in a statement. "See your dermatologist, or even your primary care physician, to check for melanoma."
Melanoma is commonly treatable if caught early -- and commonly deadly if not, so early diagnosis is crucial, Ferris said.