This article analyzes the effect of formal care unmet needs on informal
caregiving hours in Spain using two waves of the Informal Support Survey (1994, 2004). Testing for double sample selection from formal care and the emergence of unmet needs reveals that the omission of either variable causes underestimation of the number of informal caregiving hours. In the model for 2004, the selection term of the unmet needs equation is larger than that of the formal care equation, suggesting that the number of formal care recipients as a quality indicator may be confounding, if not completed with other quality indicators.