Objectives: This field study investigated the potential stress-reducing effects of exposure to real or artificial nature on patients in a hospital waiting room. Additionally, it was investigated whether perceived attractiveness of the room could explain these effects. Design: In this between-patients experimental design, patients were exposed to one of the following: real plants, posters of plants, or no nature (control). These conditions were alternately applied to two waiting rooms. Location: The location of this study was two waiting rooms at the Radiology Department of a Dutch hospital. Subjects: The subjects comprised 457 patients (60% female and 40% male) who were mostly scheduled for echocardiogram, dual-energy x-ray absorptiometry, magnetic resonance imaging, computed tomography scans, or nuclear research. Results: Patients exposed to real plants, as well as patients exposed to posters of plants, report lower levels of experienced stress compared to the control condition. Further analyses show that these small but significant effects of exposure to nature are partially mediated by the perceived attractiveness of the waiting room. Conclusions: Natural elements in hospital environments have the potential to reduce patients' feelings of stress. By increasing the attractiveness of the waiting room by adding either real plants or posters of plants, hospitals can create a pleasant atmosphere that positively influences patients' well-being. © Copyright 2012, Mary Ann Liebert, Inc. 2012.