The aim of this paper was comparison of clinical and radiographic images and presentation of treatment methods of two cases of tumours-complex odontoma and osteoma located in the posterior region of the maxilla in two adolescent patients who reported to the Department of Oral Surgery. The first lesion was detected during radiological examination which was ordered due to the absence of the first, second and third molars in the right maxilla on intraoral examination. In the second case, exposure of the bone and absence of teeth in the lateral segment of the left maxilla was noted. On intraoral examination, a fragment of exposed bone, similar in appearance to sequestrum, was visible in the place of missing tooth 27. The tumours in question differed in tissue origin: complex odontoma is a developmental odontogenic lesion, hamartomatic in type, containing haphazardly but clearly defined hard tissue; osteoma is a benign connective tissue tumour originating from bone tissue. In the case of a complex odontoma, the treatment of choice is surgical treatment to perform complete removal of the tumour. A similar approach concerns the osteoma if the tumour deforms the alveolar bone or interferes with proper tooth eruption.