The prevalence of melanonychia is approximately 1%, and it is a common symptom encountered in daily practise. However, it may also be the first symptom of melanoma of the nail apparatus. Evaluation of adult melanonychia with clinical information and clinical images is sometimes difficult for clinicians. Dermoscopic observation provides important information based on the algorithm method. Melanonychia in children requires a different approach, because dermoscopic features observed in adult nail apparatus melanoma are generally observed in benign pediatric cases.