The study of sedentary behavior is a relatively new area in population health research, and little is known about patterns of sitting time on week-days and weekend-days.To compare self-reported week-day and weekend-day sitting time with reported weekly time spent in other activities.Data were from 8,717 women born between 1973 and 1978 ('younger'), and 10,490 women born between 1946 and 1951 ('mid-age') who completed surveys for the Australian Longitudinal Study on Women's Health in 2003 and 2001, respectively. They were asked about time spent sitting on week-days and weekend-days. The women were also asked to report time spent in employment, active leisure, passive leisure, home duties, and studying. Mean week-day and weekend-day sitting times were compared with time-use using analysis of variance.Younger women sat more than mid-aged women, and sitting time was higher on week-days than on weekend-days in both cohorts. There were marked positive associations between week-day and weekend-day sitting times and time spent in passive leisure in both cohorts, and with time spent studying on week-days for the younger women. Week-day sitting time was markedly higher in women who reported >35 h in employment, compared with those who worked <35 h. In contrast, there were inverse associations between sitting time and time spent in home duties. Associations between sitting and active leisure were less consistent.Although week-day sitting time was higher than weekend-day sitting time, the patterns of the relationships between week-day and weekend-day sitting and time-use were largely similar, except for time spent in employment.