Cystic fibrosis is a congenital genetically determined disorder caused by pathogenic mutations in both alleles of the CFTR protein gene. Due to its common occurrence in the European population as well as severe and chronic course, all neonates in Poland have been screened for this disease since 2009. This enables early diagnosis and specialist care over patients. The introduction of newborn screening has also resulted in distinguishing a new category of patients with the following diagnosis: cystic fibrosis screen positive, inconclusive diagnosis or CFTR-related metabolic syndrome. This group includes children with positive newborn screen results who do not present clinical symptoms suggestive of cystic fibrosis and in whom a mutation of unknown clinical consequences is detected and/or borderline sweat test results arrive in the course of further diagnosis. The prognosis in these patients is uncertain since some of them may develop symptoms of cystic fibrosis or CFTR-related metabolic syndrome at some point in the future while other may remain fully healthy. Patients with an inconclusive diagnosis of cystic fibrosis require specialist care, which enables their further observation, diagnosis or possible verification of the diagnosis and implementation of proper treatment. This strategy gradually supplements the knowledge on mutations that have uncertain clinical consequences. It is also significant that the patient’s family understand possible consequences of a cystic fibrosis screen positive, inconclusive diagnosis (CFSPID).