Medulloblastoma is the most common type of embryonal tumour in paediatric population. This entity represents up to 4% of all intracranial neoplasms in the whole population and 20-25% of all brain tumours in children. The majority of tumours is located within vermis and fourth ventricle. Due to its frequency, histological aggressiveness, and unfavourable outcome, the treatment of children with medulloblastoma is a great clinical problem. According to the newest achievements of molecular biology, the significant heterogeneity of this tumour was confirmed. The most frequent types of molecular abnormalities detected in medulloblastoma were SHH and WNT pathways activation, MYC amplification and isochromosome i17q presence. Recently, on the basis of modern molecular analyses comprising gene expression profiling, several molecular subtypes of that tumour were described. Among them there were two subgroups connected with SHH and WNT pathways activation. SHH type medulloblastomas showed frequent CTNNB1 gene mutations and monosomy of chromosome 6. The PTCH and SUFU mutations accompanied by loss of chromosome 9 were identified in WNT type. Remaining subgroups distinguished on the basis of transcriptome analyses were not so clearly characterized and their number varied in particular molecular studies. This paper is a review of the latest data describing molecular background of medulloblastoma.