Introduction Pott's puffy tumour is characterised by frontal bone osteomyelitis accompanied by subperiosteal abscess. It can be further complicated by intracranial extension of the infectious process. Case presentation A 12-year-old boy initially presented with signs and imaging findings of pan-sinusitis. Despite antibiotic therapy, there was progressive swelling of the forehead region. Subsequent imaging studies revealed osteomyelitis of frontal bone, subcutaneous abscess and extension into intracranial space. The abscesses were surgically drained, and craniectomy for osteomyelitis was carried out. Conclusion The initial symptoms of Pott's puffy tumour can be subtle, and antibiotic use may mask the underlying sinister involvement of intracranial structures. Imaging plays an important role both in diagnosis and detection of possible intracranial complications.