Several parameters mediate the selection of treatment modality in end-stage renal disease (ESRD). The nephrology community suggests that patient preference should be the prime determinant of modality choice. We aimed to test whether ego mechanisms of defense are associated with patients’ treatment modality preferences, independent of psychological distress. In 58 eligible ESRD patients who had themselves chosen their treatment modality, we administered the Symptom Distress Checklist-90-R and the Defense Style Questionnaire. Thirty-seven patients (53.4%) had chosen hemodialysis and 21 (46.6%) peritoneal dialysis. Patients who preferred peritoneal dialysis were younger (odds ratio [OR], 0.89; 95% confidence interval [CI]: 0.804–0.988), had received more education (OR, 8.84; 95% CI: 1.301–60.161), and were twice as likely to adopt an adaptive defense style as compared to patients who preferred hemodialysis (57.1% vs 27.0%, respectively; P < 0.033). On the contrary, the latter were more likely to adopt an image-distorting defense style (35.1% vs 14.3%; P = 0.038) and passive–aggressive defenses (OR, 0.73: 95% CI: 0.504–1.006). These results were independent of psychological distress. Our findings indicate that the patient’s personality should be taken into account, if we are to better define which modalities are best suited to which patients. Also, physicians should bear in mind passive–aggressive behaviors that warrant attention and intervention in patients who preferred hemodialysis.