To explore the associations between social determinants, caregiver's network support, burden of care and their consequences in health and living conditions of informal caregivers. The socio-demographic trends regarding population ageing and changes in family models trigger an increased demand for care. Cross-sectional study based on the 2008 edition of the National Disability, Independence and Dependency Situations Survey (DIDSS-2008) conducted by the National Statistics Institute in Spain. Analyses focused on persons identified as primary caregivers who co-reside with the dependent person. The associations between social determinants of caregivers, burden of care, support network and problems attributed to informal care (impaired health, depression, professional, economic and personal issues) were estimated by fitting robust Poisson regression models. Analyses were conducted separately for women and men. The study sample included 6923 caregivers, 73% of women and 27% of men. Gender and socio-economic inequalities were found in assumption of responsibilities and burden of caring for dependents, which tend to fall more on women and persons of lower socio-economic level, who in turn have less access to formal support. These aspects translate into a higher prevalence of health, professional, economic and personal problems. The study highlights gender and socio-economic inequalities in informal caregiving and its negative consequences. These findings may be useful in the design of policies and support programmes targeting the most affected groups of informal caregivers.