Purpose To investigate whether psychosocial job demands (work pace and quantitative demands) and job resources (influence at work and quality of leadership) predict long-term sickness absence (LTSA) for more than three consecutive weeks in four occupational groups. Methods Survey data pooling 39,408 respondents were fitted to a national register containing information on payments of sickness absence compensation. Using multi-adjusted Cox regression, respondents were followed for an 18-month follow-up period to assess risk of LTSA. Results In the entire study population, low and medium levels of influence at work and low quality of leadership predicted a significantly increased risk of LTSA, whereas medium levels of quantitative demands predicted a significantly reduced risk of LTSA. For employees working with clients and for office workers, low and medium influence at work associated with a significantly increased risk of LTSA. For employees working with clients, low quality of leadership predicted a significantly increased risk of LTSA. For manual workers, low influence at work predicted a significantly increased risk of LTSA and medium quantitative demands were associated with a significantly reduced risk of LTSA. For employees working with customers, medium quantitative demands predicted a significantly reduced risk of LTSA. Finally, in predicting LTSA, we found significant interaction effects between job demands and job resources. Conclusions The study indicates that a lack of job resources—particularly influence at work—are more important predictors of LTSA than high job demands.