The past few years have seen the advent and proliferation of Voting Advice (or Aid) Applications (VAAs), which offer voting advice on the basis of calculating the ideological congruence between citizens and political actors. Although VAA data have often been used to test many empirical questions regarding voting behaviour and political participation, we know little about the approaches used by VAAs to estimate the positions of political parties. This article presents the most common aspects of the VAA approach and examines some methodological issues regarding the phrasing of statements, the format of response scales, the reliability of coding statements into response scales and the reliability and validity of scaling items into dimensions. The article argues that VAAs have a lot of potential but there is also much space for methodological improvements, and therefore concludes with some recommendations for designing VAAs.