Research on children's ideas about biological phenomena showed that their interpretations of natural phenomena often differ from those of scientists. The purpose of this study was to investigate children's ideas about animal breathing systems. This study was descriptive in nature and consisted of a cross age and cross cultural design involving the collection of qualitative data from a total of 549 children from two distinct countries, Slovakia (n = 248) and Turkey (n = 301). The results revealed that understandings of invertebrates breathing systems were generally poorer than understandings of vertebrates breathing systems. Turkish children acquired better scores than Slovakian children. Although some children were able to identify breathing organs of animals, they had difficulties with describing how breathing works.