Dermatoscopy is a simple and non-invasive diagnostic method which allows visualisation of the structures and their colours situated within the epidermis and dermis that are invisible with the naked eye due to multiple magnification. Since 1920 a significant progress of the technology of equipment and scope of the performed diagnostics has been made. Currently applied dermatoscopy is the most frequently method used to assess the lesions and diseases of the skin, hair, nails and microcirculation. The objective of this paper is to demonstrate dematoscopy’s wide usefulness as a diagnostic method in the cosmetologist’s cabinet. The technique of examination, basic principles and diagnostic algorithms as well as selected diseases located within the smooth skin, hairy skin of the head and nail plates were presented and described. Among them the following were differentiated: melanocytic and non-melanocytic lesions, inflammatory diseases of the skin caused by microbes, non-infectious inflammatory skin diseases as well as ailments of the hairy skin of the head and nail plates that can be diagnosed by a cosmetologist during his/her work in the cabinet and, also, in other institutions dealing with health and beauty promotion. Nowadays dermatoscopy as a diagnostic method is applied to differentiate and assess melanocytic and non-melanocytic eruptions, which constitutes the foundation of prophylaxis of melanoma. Furthermore, it is a procedure that considerably supports diagnostic validity and helps to classify the ailments of various etiology and location. A dermatoscope in the hands of properly trained cosmetologist or physician constitutes a reliable diagnostic tool. The analysis performed with its help frequently protects a client/patient from the loss of health and it may even save his life.