Chronic appendicitis is a pathologic condition caused by a slowly developing, flaccid and long-lasting inflammatory process in the appendix of the cecum. A 7-year-old child with chronic appendicitis and appendix penetration into the posterior wall of the bladder was treated at the surgical department of Vladimirovsky Moscow Region Clinical Institute. Such a combined pathology caused some difficulties in diagnostics. Chronic appendicitis is considered as an independent nosological form and can be masked by various surgical conditions.