Paraneoplastic dermatoses have a particular interest to the dermatologist since oncological diseases are on the rise and spread, as well as they are combined with various dermatoses. The analysis of existing diagnostic methods of paraneoplastic pemphigus is presented. In parallel with acantholysis, caused by autoimmune reactions, cell-mediated immune response is noted in the epidermis in paraneoplastic pemphigus, that leads to the keratinocytes apoptosis with T-cell infiltration in the epidermis. Oncological disease may begin to develop either earlier, or simultaneously with bullous dermatosis, or after the onset of pemphigus. Mucous membrane lesions are usually the first clinical manifestations of paraneoplastic pemphigus. Erosive foci are visualized on the oral mucosa, before which vesicles or bullae rarely appear. Lesions can spread to the vermillion border and associated with a significant pain. Next, skin lesions are detected, rapidly complicating by the secondary infection. The possibility of autoimmune response development from viscelar organs in paraneoplastic pemphigus has been noted. DIF confirms the diagnosis.