Background: Religiosity and spirituality have been found to be substantially associated with a variety of mental health and illness parameters. However, relevant empirical evidence is sparse, and more research is needed in order to further understand what role religiosity/spirituality plays in the development, progression and healing process of a psychiatric disease. Thus, the purpose of this study was to find out more information about the religious/spiritual needs of anxious/depressive inpatients. Sampling and Methods: A total sample of 200 well-characterized anxious/depressive inpatients was investigated. Results were compared to those from an adjusted group of healthy individuals (n = 200). A newly developed Multidimensional Inventory for Religious/Spiritual Well-Being was applied to both groups, together with established psychiatric measures (e.g. Beck Depression Inventory). Results: Of the dimensions measured, Hope and Forgiveness turned out to be the strongest negative correlates of anxious/depressive symptoms (p < 0.001). Moreover, a lower degree of Hope (p < 0.001) and Experiences of Sense and Meaning (p < 0.01) was found in the patient group compared to healthy controls. In accordance with the literature, religiosity was confirmed to be a substantial suicidal buffer (p < 0.01). Conclusions: Our results account for a more comprehensive psychiatric evaluation, emphasizing in particular the role that religiosity/spirituality plays in overall well-being. Furthermore, religious/spiritual well-being might be considered an important resource to explore, in particular for affective mentally disordered patients.