This study examined the supplemental value of a cognitive coping skills training when added to an operant-behavioral treatment for chronic low-back pain patients. The complete treatment package (OPCO) was compared with an operant program + group discussion (OPDI) and a waiting-list control (WLC). After the WL period, the WLC patients received a less protocolized operant program usually provided in Dutch rehabilitation centers (OPUS). Regression analyses showed that, compared with WLC, both OPCO and OPDI led to less negative affect, higher activity tolerance, less pain behavior, and higher pain coping and pain control. At posttreatment, OPCO led to better pain coping and pain control than OPDI. Calculation of improvement rates revealed that OPCO and OPDI had significantly more improved patients than OPUS on all the dependent variables. The discussion includes findings regarding treatment credibility, compliance, and contamination bias.