In this diploma essay are described causes of formation, clinical characteristics, diagnosis and treatment of squamous cell carcinoma with one clinical case of squamous cell carcinoma in one dog who was hospitalised at the Internal Diseases Clinic of the Faculty of Veterinary Medicine in Zagreb where clinical and laboratory processing and treatment was performed. When a tumor diagnosis had been given, the owners of the dog agreed to the treatment so the dog was treated and monitored for 391 days at the Internal Diseases Clinic of the Faculty of Veterinary Medicine in Zagreb. After a tumor diagnosis had been given, the dog was subjected to a surgical procedure and the radiation therapy was recommended. Considering that the radiation therapy is not available in Croatia, because of financial reasons of the owners, the treatment was continued with chemotherapy. During that 391 days, the dog was treated with Cisplatin, then Endoxan and Luborum (piroxicam) and then Vinblastin and Doxorubicin were put into treatment. During that 370 days, the patient was in good general condition with a completely preserved quality of life and the tumor was under control. After that, the progression of the disease appeared so on the 391. day the dog was euthanised in respiratory crisis consequntly metastasis of lungs.