The effort of this manual is to give information on the types of cancer, problems caused by a tumor, the possibilities of anticancer treatment, complications associated with this treatment and their influence. The pivotal theme of the book The Patient Guide to Oncological Treatment, which is devoted to this publication, is the problem of nutrition in cancer and during anti -tumor therapy. Insufficient or inappropriate composition of the diet may worsen the general condition of the patient and thus worsen the course and often the results of treatment. The tumor or anticancer treatment itself can cause eating disorders or disrupt and change the processes of digestion and metabolism. The patient guide guide oncological treatment is divided into a theoretical part, where you will find general information on cancer, anticancer treatment, organ symptoms that can cause a tumor or antitumor treatment. The second part of the manual is focused practically, you will find advice on how to behave in the case of problems complicating food intake and processing.