For the diagnosis and therapy an important thing is to analyse a relationship between mental state and the somatic disease. In the case of a patient with somatic disease and neurotic disorder, the process of diagnosis and treatment is difficult due to:– similar symptoms occurring in both neurotic disorders and somatic diseases; – denial mechanism: the patient hides disturbing symptoms and avoids tests and medical consultations. Fear accompanying neurotic symptoms can cause an intensification of functional disorders, which can intensify symptoms of somatic disease. From the other side, fear can be a psychological reaction to somatic disease and can sustain neurotic disorders. Psychotherapy via cancellation of fear can contribute to the improvement of the mental state and at the same time it can be helpful in the treatment of somatic disease. Common biological and psychosocial factors affect the appearance and maintain both the somatic disease and neurotic disorder. Bilateral relation occurring between those disorders are briefly presented.