Background. In recent decades an increase in newly diagnosed celiac disease in both schoolchildren and adults has been observed. Celiac disease is the most common genetically determined disease of the gastrointestinal system and is most frequently diagnosed in the first three years of life and between the ages of 44 and 64. Asymptomatic, silent, and late-onset celiac disease are the predominant forms. Objectives. Analysis of the frequency of clinical symptoms and coexisting diseases in schoolchildren and adults with diagnosed celiac disease. Material and Methods. The study comprised 59 children aged 7 to 18 years (mean: 12.5 years) and 52 adults aged 19 to 75 years (mean: 32 years) in whom celiac disease was diagnosed based on histological study of intestinal specimens and positive serologic tests (EmA, tTG). Clinical symptoms, nutritional status, and coexisting diseases were analyzed in all the patients. Results. Low body mass (69.5%), abdominalgia (59.3%), recurrent diarrhea (39%), and anemia (28.8%) were most frequently observed in the children. The most frequent symptoms in the adults were anemia (80.7%), flatulence (76.9%), increased aminotransferase activity (AST and ALT, 73.1%), chronic diarrhea (59.6%), and low body mass (59.6%). Conclusions. Deficiency in body mass and height as well as abdominal pains and recurrent diarrhea were the most frequent symptoms in the schoolchildren with celiac disease. In adults the most frequently observed were anemia, chronic diarrhea, flatulence, and increased AST and ALT activity as well as more frequent occurrence of diabetes mellitus, diseases of the thyroid gland, and osteoporosis (Adv Clin Exp Med 2009, 18, 2, 153 - 158).