Cervical cancer occurs most often in under-screened women. In this nationwide register study, we described differences in sociodemographic characteristics between passive and active non-participants and examined socio-demographic characteristics, reproductive history, and mental and physical health as potential determinants for passive non-participation compared with participation in the Danish cervical cancer screening program. Screening history in women aged 23–49 years invited for cervical cancer screening in 2008–2009 was retrieved from the Danish Pathology Databank with information about dates of invitation and unsubscription. We identified participants (n=402,984), active non-participants (n=10,251) and passive non-participants (n = 63,435) within four years following baseline invitation and retrieved data about the study population from high-quality registries. We examined differences in socio-demographic characteristics of passive and active non-participants, and used multiple logistic regression analyses to identify potential determinants of passive non-participation. We found that active and passive non-participants differed in relation to socio-demography. When compared with screening participants, the odds of passive non-participation was increased in women who originated from less developed countries; were unmarried; had basic education or low income; had four or more children; smoked during pregnancy; had multiple induced abortions; or had a history of obesity, intoxicant abuse or schizophrenia or other psychoses. In conclusion, in this nationwide, prospective, population-based study, differences in socio-demographic characteristics between passive and active non-participants were found. Furthermore, sociodemography, reproductive history, and mental and physical health were determinants for passive non-participation. Addressing inequalities in screening attendance may help to further decrease the incidence of and mortality from cervical cancer.