Underdiagnosis of childhood asthma is a well known problem in many countries. In Poland the estimated occurrence of this problem reaches 50% and is similar to fi ndings published in foreign literature. The causes of the problem are not unequivocally recognized and are addressed by few authors. Among potential causes there are circumstances related to organization and practice of pediatric health care, including application of standard diagnostic criteria of asthma, availability of diagnostic tests, nozologic preferences, etc. Another category of circumstances in charge of underdiagnosis of childhood asthma stems from environmental infl uences, including family-related factors. Findings published in foreign literature show that underdiagnosis is more frequent in children of low socio-economic status, in rural setting or in families burdened by stress. Evidence however is far from being complete. There is a lack of Polish data on the subject and it remains unknown to what extent underdiagnosis of childhood asthma in this country is related to the above mentioned factors. Scientifi c investigation into the problem is necessary for a number of reasons and justifi es implementation of subject-oriented epidemiological studies. Identifi cation of factors associated with an increased probability of underdiagnosis of childhood asthma should facilitate planning of proper preventive measures, above all involving screening programs addressed to selected groups of population.