The use of ChatGPT has steadily increased over the years following its launch. This study evaluated ChatGPT-4o’s diagnostic accuracy in dermatological education case studies, comparing Free Answer and Multiple Choice formats, and assessing the impact of input data. Results showed a better performance in the Free Answer format, as opposed to Multiple Choice. Furthermore, adding patient data to the input images did not improve accuracy. These findings suggest that while ChatGPT-4o can serve as a second-opinion tool in dermatological education, it can do so by supporting, not replacing, the critical thinking process the students should perform when exercising diagnostic capabilities. Proper regulation is needed to ensure ethical and effective implementation of Generative AI in medical education.