OBJECTIVE: To evaluate whether patients with RA who belong to the spectrum of fibromyalgic RA (FRA) have an impaired response to treatment measured by traditional activity scores. METHODS: Patients from the ESPOIR cohort were analysed. This prospective cohort included 813 patients with early arthritis not initially receiving DMARDs. Among the 697 patients who met RA classification criteria, we studied two groups, one with and the other without FRA. The following endpoints were compared at 6, 12 and 18 months using a mixed linear regression model: 28-joint DAS (DAS28), Simple Disease Activity Index (SDAI), Clinical Disease Activity Index (CDAI) and HAQ. In addition, attainment of low disease activity (LDA; DAS28 <3.2) and remission (DAS28 <2.6, SDAI <3.3, CDAI <2.8) at these time points was analysed. RESULTS: Patients with FRA (n = 120) had higher DAS28, SDAI, CDAI and HAQ scores than patients with RA and no fibromyalgic characteristics (n = 548). DAS28 and other DASs started out higher in subjects with FRA, and while they improved to a similar extent to in the isolated RA group, they remained consistently higher among FRA patients. Achievement of LDA and remission was significantly less likely in subjects with FRA. CONCLUSION: Patients with FRA and RA will have a similar response to treatment according to the decrease in indexes of disease activity, but may miss the target of remission or LDA.