In Spain, female labour force participation is among the lowest in Europe. This paper analyzes the extent to which female labour force participation is affected by the cost of formal childcare. Both decisions, labour force participation and formal childcare use, are jointly considered by means of a bi-variate probit model that accounts for the sample selection. Based on data from the Spanish Time Use Survey, the study indicates that Spanish mothers� labour force participation is very elastic to changes in childcare costs.