Early diagnosis of cystic fibrosis, which is established after a correct classification of manifestations of the disease during the first 6, respectively 12 months of life and an immediate beginning of therapy, favorably influences the course of the disease. Unfortunately, the experience of the authors indicates that the situation in the Czech Republic has deteriorated over the last years. The physicians do not pay attention to signs of the disease, neglect the statě of nutrition as well as clubbing of the fingers. They also neglect the information of the mothers about salty sweat, prolapse of rectum or character of stools. In the diagnostics of gastrointestinal manifestations the physicians more often consider celiac disease or intolerance of some components of food, in analysis of respiratory complaints they pay attention to asthma, disorders of immunity or repea-ted infections of respiratory pathways. The diagnostic errors we háve witnessed over the last years, unfortunately seriously affect the patients. We háve demonstrated that patients diagnosed until their age of one year demonstrate better lung functions at their 8 years of life than patients having been diagnosed later. A latě diagnosis results in unfavorable psychological effects. The parents are then lacking a possibility of prenatal diagnosis and there is a possibility of their giving birth to another child with cystic fibrosis. The given experience with failing clinical dia¬gnostics reveal a reál need of newborn screening of cystic fibrosis in the Czech Republic and resulted in our pilot study of such screening aimed at verification of feasibility and efficiency of such investigation. There is a need of pediatricians to devote increasing attention to differential diagnostics until a full scale newborn screening is introduced.

        Key words: cystic fibrosis, late diagnosis, lung functions, state of nutrition, clubbing of the fingers, newborn screening