BACKGROUND: Potential treatment-related neurotoxicity and the indolent course of the disease mainly feed the controversy concerning the optimal timing of surgery and radiotherapy in meningioma patients. OBJECT: To quantify the additional negative effects of conventional radiotherapy compared to surgery alone on neurocognitive functioning and health-related quality of life (HRQOL) in patients with WHO grade I meningiomas. METHODS: Neurocognitive functioning and HRQOL (SF36, EORTC-BCM20) were assessed in consecutive patients (1999-2005) with WHO grade I meningiomas at least 1 year after surgical treatment in two centers for brain tumor patients. Subsequently, we selected all patients who underwent surgery and conformal external beam fractioned radiotherapy (n=18) and matched these patients for age, sex, and educational level with the same number of patients who had had surgery only (n=18), as well as with the same number of healthy controls. RESULTS: No significant differences in neurocognitive functioning were found between the two meningioma patient groups; however, even meningioma patients who were treated with surgery only had a significantly lower neurocognitive functioning than healthy controls. Meningioma patients who were treated with surgery and radiotherapy had significantly lower HRQOL scores than meningioma patients who were treated with surgery only, who had HRQOL ratings comparable with healthy controls; these differences, however, disappeared after correction for the duration of disease. CONCLUSIONS: In contrast with conventional thinking, long-term neurocognitive functioning was significantly impaired in our meningioma patients. Additional radiotherapy following surgery, however, does not have additional deleterious effects on neurocognitive outcome in these patients.