Purpose: Mental distress is common in persons experiencing low back pain and who are sick-listed or at risk of being sick-listed. It is, however, not known how mental distress measured by the Symptoms Check List-90 differs between patients with low back pain and the general population. The objective of this study was to compare mental symptoms and distress as measured by the Symptoms Check List-90 in sick-listed or at risk of being sick-listed patients with low back pain with a population-based control group. Methods: Mental distress was compared in a group of patients with low back pain ( n=770) and a randomly selected population-based reference group ( n=909). Established Danish cut-off values for mental distress were used to evaluate the mental distress status in the low back pain and control group and logistic regression was used to calculate odds ratios for the Global Severity Index and the symptom scales of the Symptoms Check List-90 while controlling for baseline demographic differences between the groups. Results: Group mean scores showed that all symptom scales and the Global Severity Index for both sexes were statistically elevated in the low back pain group, except for interpersonal sensitivity in women. When the scores were dichotomized to cases and non-cases of mental distress, a significantly higher prevalence of cases was observed in the low back pain group compared to the reference group on all symptom check list scales, except for paranoid ideation for both sexes and interpersonal sensitivity for women. The biggest between-group difference was observed for the somatization symptom scale. Conclusions: Low back pain patients who are sick-listed or at risk of being sick-listed, are more mentally distressed compared to a randomly selected sample of the general Danish population. Self-reported symptoms of somatization, anxiety, phobic anxiety, obsessive-compulsive, depression and hostility are all more common among patients with low back pain compared to the general population.