This study investigates whether the two dimensions of illness flexibility at work, adjustment latitude and attendance requirements are associated to sickness absence and sickness attendance. Adjustment latitude describes the opportunities people have to reduce or in other ways change their work-effort when ill. Such opportunities can be to choose among work tasks or work at a slower pace. Attendance requirements describe negative consequences of being away from work that can affect either the subject, work mates or a third party. In a cross-sectional design data based on self-reports from a questionnaire from 4924 inhabitants in the county of Stockholm were analysed. The results showed that low adjustment latitude, as predicted, increased women's sickness absence. However, it did not show any relation to men's sickness absence and men's and women's sickness attendance. Attendance requirements were strongly associated to both men's and women's sickness absence and sickness attendance in the predicted way. Those more often required to attend were less likely to be absent and more likely to attend work at illness. As this is the first study of how illness flexibility at work affects behaviour at illness, it was concluded that more studies are needed.