The aim of the thesis is a review and systematic analysis of current knowledge about the effectiveness of swimming on human health, in this case on the respiratory tract due to the circumstances in which this sport takes place. Global swimming has positive effects on lung function, but due to the conditions in which it takes place, the effects are sometimes reduced or imperceptible, but some studies claim the opposite. People with allergies and respiratory diseases are often recommended swimming as therapy for their health condition because the health benefits of indoor swimming are believed to far outweigh the risks associated with indoor swimming. In this paper, research was conducted using a questionnaire under the name Changes in lung function caused by swimming. The questionnaire is divided into 3 parts. The first part related to general information about the individual's condition, the second part was called the basic asthma questionnaire and the questions were related to asthma, while the third part was oriented towards rhinitis. The questionnaire did not have correct or incorrect answers, so we asked respondents to answer honestly. A total of 205 swimmers completed the questionnaire. Thirteen questionnaires were dropped due to incomplete completion of the questionnaire, so the total number was 193 respondents (n=193). Questionnaires were distributed at Croatian swimming association development camps (Region 1, 2, 3 and 4), but also in clubs during training. The number of respondents by region is: Region 1 (N = 29), Region 2 (N = 68), Region 3 (N = 42), Region 4 (N = 53). Out of 193 respondents, 8 of them declared that they have asthma. In the following, 7 questions are selected in order to give us a more detailed insight into the state of lung functions of Croatian male and female swimmers.