Onychomycosis in children is rare and in different countries prevalence varies from 0.2 to 0.4%. Herein, we describe clinical features, mycology and treatment options of onychomycosis in children, based on 15 cases seen at our department from 2002 to 2007 and on a review of the literature. Nail invasion by fungi in children may occur in both healthy and immunodepressed individuals, and is usually due to dermatophytes, mostly Trichophyton rubrum and Trichophyton interdigitale. Predisposing factors to dermatophyte onychomycosis (i.e., family history for onychomycosis, contact with fungi in the environment and sports activities) are quite common in children, being present in 53% of children with onychomycosis. True Candida onychomycosis in children may be mainly seen in three instances: in premature newborns, where it is due to incomplete development of the immune system; in children affected by chronic mucocutaneous candidiasis; and in children with iatrogenic immunodepression.