Objectives/Hypothesis: headache is a common symptom in the general population. Although it could be a symptom of acute sinusitis, chronic sinusitis is not considered as a usual cause of headache. In addition, vascular pain may be associated with related autonomic symptoms in the sinonasal region. These can be confusing and lead to an incorrect diagnosis of sinusitis. Study Design: A prospective cross-sectional study.Methods: Fifty-eight patients with diagnosis of “sinus headache” by primary care physicians were evaluated. Exclusion criteria were: previous diagnosis of migraine or tension-type headache; evidence of sinus infection during the past six months; and the mucopurulent secretions during the physical examination. After comprehensive otorhinolaryngologic and neurologic evaluations, an appropriate treatment was started according to the final diagnosis and the patient was visited monthly over a period of six months. Results: The final diagnoses were migraine, tension type headache, and chronic sinusitis with recurrent acute episodes in 68%, 27%, and 5% of the patients, respectively. Seventy-three percent of the patients with tension type headache and 66% of the patients with migraine had received recurrent antibiotic therapy. Sinus endoscopy had been performed in 26% of patients. Therapeutic nasal septoplasty had been performed for 16% of the patients with a final diagnosis of migraine, and 13% of the patients with tension type headache.Conclusion: Many patients with self-described or primary care physician labeled “sinus headache” have no sinonasal abnormalities. Instead, most of them meet the IHS criteria for migraine or tension headache.