Objective This study aims to discuss factors specific to diabetics in the diagnosis and treatment of onychomycosis. Discussion Onychomycosis has the potential to cause severe complications in diabetics and should be treated promptly. The existence of comorbid conditions and potential for drug-drug interactions complicates the selection of an appropriate treatment regimen. The role of Candida in onychomycosis is controversial but may be of increased significance in the diabetic population due to an underlying vulnerability to this organism. Conclusions Terbinafine is an excellent choice in diabetics due to its low risk of drug-drug interaction and proven efficacy against the typical pathogens that cause onychomycosis. Itraconazole, while an effective treatment for onychomycosis, is not a first-choice therapy due to its black-box cardiac warning and numerous drug interactions. Larger studies are needed in diabetics to determine the frequency of candidal nail infections. © 2009 European Academy of Dermatology and Venereology.