The present study focused on the evaluation of the effects of operant behavioural (OBT) and cognitive behavioural (CBT) treatments for fibromyalgia syndrome (FMS). One hundred and twenty-five patients who fulfilled the American College of Rheumatology criteria for FMS were randomly assigned to OBT (n = 43), CBT (n = 42), or an attention-placebo (AP) treatment (n = 40) that consisted of discussions of FMS-related problems. Assessments of physical functioning, pain, affective distress, and cognitive and behavioural variables were performed pre-treatment and post-treatment as well as 6 and 12 months post-treatment. Patients receiving the OBT or CBT reported a significant reduction in pain intensity post-treatment (all Fs > 3.89, all Ps < 0.01). In addition, the CBT group reported statistically significant improvements in cognitive (all Fs > 7.95, all P < 0.01) and affective variables (all Fs > 2.99, all Ps < 0.02), and the OBT group demonstrated statistically significant improvements in physical functioning and behavioural variables (all Fs > 5.99, all Ps < 0.001) compared with AP. The AP group reported no significant improvement but actually deterioration in the outcome variables. The post-treatment effects for the OBT and CBT groups were maintained at both the 6- and 12-month follow-ups. These results suggest that both OBT and CBT are effective in treating patients with FMS with some differences in the outcome measures specifically targeted by the individual treatments compared with an unstructured discussion group. The AP group showed that unstructured discussion of FMS-related problems may be detrimental.