Background. It has been suggested that panic disorder can cause or contribute to hypertension or resistance to antihypertensive drugs. Objective. To compare the prevalences of panic disorder, panic attacks, anxiety and depression between patients with resistant hypertension and age- and sex-matched patients with non-resistant hypertension. Design. A case-control study of patients attending the Sheffield Hypertension Clinic, using self-completed postal questionnaires to assess panic disorder, anxiety and depression. Patients. Cases with resistant hypertension were defined as patients who presently or previously had systolic blood pressure above 160 mmHg or diastolic blood pressure above 90 mmHg despite the use of three or more antihypertensive agents at full dose. For each of 136 cases, one control with non-resistant hypertension, defined as controlled to ≤ 160/90 mmHg by one or two antihypertensive agents, was identified by a bias-free method. Cases and controls were matched for age and sex. Main outcome measures. Lifetime and current prevalence of panic attacks, the prevalences of panic disorder, anxiety and depression by Hospital Anxiety and Depression Scale scores, and the severity and frequency of panic attacks. Results. Of the resistant hypertensive patients, 33% had experienced a panic attack compared with 39% of the control non-resistant hypertensives (resistant-non-resistant -6%, 95% confidence interval -19 to +7%). Twelve per cent of the resistant patients and 14% of controls fulfilled the criteria for a current or previous diagnosis of panic disorder (resistant-non-resistant -2%, 95% confidence interval -11 to +7%). There were also no significant differences between the groups in the prevalences of current panic attacks, panic attacks rated as moderate or worse, spontaneous panic attacks and in the frequency of panic attacks. There remained no significant difference between the groups for panic attacks and panic disorder when the analysis was limited to those patients who had idiopathic hypertension. The two groups did not differ significantly in scores for anxiety and depression measured by the Hospital Anxiety and Depression Scale. Conclusion. We observed no differences in the prevalences of panic, anxiety and depression between patients with resistant hypertension and non-resistant controls. These factors are probably not implicated in resistance to drug treatment. However, the prevalences of panic disorder and panic attacks were remarkably high in both groups of patients attending a hospital hypertension clinic. The relationship between panic disorder and hypertension deserves further study in a general hypertensive population.