BACKGROUND: Although there has been great development in the diagnosis and treatment of sinusitis, a cerebral abscess and Pott´s tumor are serious complications. CASE REPORT: Patient 1 was a 16-year-old boy who presented to the emergency department with a headache, fever, and bulging frontal bone; was clinically treated with oral antibiotics; and demonstrated improvement. After stopping treatment, the bulge recurred with a worsening of his general condition, after which he was referred to the Department of Otorhinolaryngology. He had edema and fluctuation in the frontal region. A nasal endoscopy revealed polyps in the right middle meatus, and a computed tomography of the paranasal sinuses revealed opacification of the right maxillary, ethmoid, and frontal sinuses and signs of frontal osteomyelitis within a bony fistula. He underwent endoscopic sinus surgery (FESS), with external access to the frontal bone and debridement and drainage of the abscess, and was then treated with intravenous antibiotic therapy, after which he was in remission. Patient 2 was a 17-year-old boy who developed periorbital pain, fever, headaches, and worsening edema, after treatment for conjunctivitis and influenza. In the Department of Otorhinolaryngology, a computed tomography of the paranasal sinuses showed opacification of the left frontal, maxillary, and ethmoid sinuses but no evidence of bone erosion in the orbital region; however, after a computed tomography revealed a left extradural abscess, the patient was referred to the neurosurgical service. Drainage of the brain abscess and endoscopic sinus surgery were conducted, with symptom resolution after an antibiotic cycle. CONCLUSION: Otorhinolaryngologists should remain alert to cases of sinusitis that evolve poorly with clinical treatment and should consider aggressive multidisciplinary treatment, including emergency treatment.