Classification is the arrangement of objects such as e.g. organisms, ideas, or information into groups. Its purpose is to make things easier to identify, describe, organize, find and study. Although classification itself is meant to help people to unify or clarify objects they are interested in, publications show that students might find it difficult to classify plants, animals and other organisms. The goal of the study has been to investigate Polish students’ conceptions and attitudes towards animal classification and reveal the gaps between these and current scientific knowledge. The study has been conducted by surveys and in-depth interviews of 34 pupils, from primary schools. The research shows that students have similar conceptions about animal classification and also that children see the purpose behind animal classification but find it hard to apply in practice. Moreover, students were using different factors to distinguish animal classes from the ones used by scientific community. For example, they differentiated animals on the basis of: food they consume, respiratory system and utility for humans. Authors suggest that more stress should be put on these aspects during designing lessons about animal classification.