The aim of this open label trial was to evaluate mirtazapine tolerability and effectiveness in controlling symptomatology of patients with panic disorder. Forty-five patients with panic disorder, with or without agoraphobia, 11 of them with a comorbid diagnosis of major depression, were included. Patients were assessed with a structured psychiatric interview and their symptomatology evaluated with specific psychometric scales. Three study participants dropped out due to adverse events. Mirtazapine was administered at an established dose of 30 mg daily for 3 months. Patients were assessed at weeks 2 and 4, and then at monthly intervals. All psychometric measures showed statistically significant reductions in total scores at the rated time points, with a pronounced decline in number and intensity of panic attacks and anticipatory anxiety throughout the study. Mirtazapine was well tolerated as signified by the low discontinuation rate (6.3%), and all patients showed a significant symptomatic improvement. The improvement did not appear to be linked to the concurrent presence of a depressive illness.