This population-based study investigated prospectively collected absence for respiratory illness data in two types of formal childcare (centre day care and family day care) in Perth, Western Australia, and factors associated with such absence.Methods All centres (n = 11) and 95% of family day care caregivers (n = 130) selected at random from licensing lists agreed to participate. Demographic details were obtained from a parental questionnaire and absences were recorded prospectively. Characteristics of the child and family were described using univariate odds ratios (OR) with 95% confidence intervals (CI). Multivariable analysis including generalized estimating equations was used to investigate having at least one absence for respiratory illness, having two or more absences, and having six or more absences.Results No statistically significant difference between care types for having had at least one absence episode for respiratory illness (OR 1.37, 95% CI 0.92–2.04) was found. Children who attended care for more days per week (OR 1.40, 95% CI 1.26–1.56) and those in the study for more weeks (OR 1.03, 95% CI 1.01–1.05) were more likely to be absent for respiratory illness. Those children in care for a greater number of hours per day were less likely to be absent (OR 0.88, 95% CI 0.80–0.97). Family history of bronchitis was also associated with absence for respiratory illness (OR 1.86, 95% CI 1.32–2.63).Conclusions Statistically significant factors which had an impact on absence for respiratory illness were primarily those relating to the time spent in childcare and to family history of bronchitis.