This article assesses the influence of populist parties on two central aspects of democracy – participation and representation. In line with traditional theories on populism and democracy, we argue that populist parties have a positive effect on electoral turnout and the equality of participation. This effect, however, is moderated by the party's role in government or opposition as well as their host-ideology, i.e. left, centre or right. We argue that populist parties also have a positive effect on substantive representation, but that this effect is strongly dependent on their host-ideology. We test these arguments with lagged dependent variable models using data from 31 European countries from 1990 until 2014. We find mixed support for our theoretical expectations.