Aim <p>Preserving work ability and preventing disability pension is crucial. Low back pain is one of the main reasons for sick leaves and disability pensions. The aim of this study was to investigate the relationship between Work Ability Index (WAI) scores, depressive symptoms and low back pain.</p> Subject and methods <p>In this cross-sectional, population-based study, 922 randomly selected Finnish men between 20 and 40 years of age filled in a questionnaire booklet. The questionnaire booklet contained the Oswestry Disability Index (ODI), Work Ability Index (WAI) and Beck’s Depression Index (BDI) and some other general health related questionnaires. All the men were actively working. Work Ability Index and depression scores were calculated for men suffering low back pain and men without low back pain symptoms. The results were expressed as means and standard deviations (SD) or 95% confidence intervals (95% CI).</p> Results <p>Work ability was significantly lower among the men having low back pain symptoms (mean WAI score 38, 95% CI 35–40) than among those with no low back pain (mean WAI score 44, 95% CI 43–47). Depressive symptoms decreased the WAI score even more (mean 31, 95% CI 29–35). Decreased work ability, with a WAI score 37 points or lower, was present among 35% of the men having low back pain problems and 67% of the men suffering both low back pain and depressive symptoms had decreased work ability according to the WAI score.</p> Conclusion <p>Low back pain appears to reduce work ability among working men, and depressive symptoms even further reduces the WAI scores. There is a positive correlation between low back pain and depressive symptoms. Previous studies have shown that decreased work ability appears to have a correlation with the prevalence of unemployment and long sick leaves. This study emphasises the importance of screening low back pain and depressive symptoms among working men to sustain adequate work ability.</p>