Background. Better insight into frequent comorbidities in patients with chronic (= 3 months) low back pain (LBP) may help general practitioners when planning comprehensive care for these patients. Objective. To prospectively study the prevalence of psychological, social, musculoskeletal and somatoform disorders in patients presenting with chronic non-specific LBP to general practitioners, in comparison to a contrast group of patients consulting in the same setting. Methods. This case-control study is embedded in a historical cohort, based on a primary care practice-based research network. All the health problems presented by the patients were prospectively coded according to the international classification of primary care between 1996 and 2013. The prevalence of psychological, social, musculoskeletal and somatoform disorders presented by the adult patients from 1 year before the onset of chronic LBP to 2 years after onset was compared to that of matched patients consulting without LBP, using conditional logistic regressions. Results. The 1511 patients with chronic LBP more often presented musculoskeletal disorders than the contrast group during the year before the onset of LBP and during the second year after it, with odds ratios (95%confidence intervals) of 1.39 (1.20-1.61) and 1.56 (1.35-1.81), respectively. They did not more often present psychological, social or non-musculoskeletal somatoform disorders. Conclusions. General practitioners should consider all the musculoskeletal symptoms when caring for patients with chronic LBP. Rather than systematically screening for specific psychological, social or somatoform disorders, they should consider with the patient how LBP and any type of potential comorbidity interfere with his/her daily functioning.