This paper explores preschool children's understanding of the concept of number, with a focus on five-year-olds. The research aims to investigate the numerical abilities of preschool children. The sample consisted of 100 five-year-olds from private and public preschool institutions in the Zenica-Doboj Canton in Bosnia and Herzegovina, 50 children from public institutions and 50 from private institutions. The children answered 10 questions related to counting up to 10, reading and writing numbers from 1 to 10, and counting backwards from 10 to 1. The aim was to determine their understanding of the concept of number, numerical sequences, counting elements of a given set, recognising numerical notations and writing numbers, while also identifying possible differences based on gender and the type of preschool institution they attended. The results of the research may provide insight into the development of numerical abilities in preschool children and may be useful for future educational strategies.