The selection of electoral candidates by political parties, an intraparty process taking place before the elections, directly influences the composition of parliaments. Surprisingly little is known on the rationale behind this ‘choice before the choice’. This project aims first at understanding the selection criteria used by parties to choose their candidates. On what basis do they make their candidate selection choices? Parties may rely on candidates’ characteristics, such as their positions, skills, popularity and/or experience. I consider criteria at both the individual level of each candidate and at the aggregate list level. Second, the project intends to explain the influence of electoral systems on these selection criteria: can electoral rules explain variation? I hypothesize that the more open the system, the more selectors value individual over list characteristics. Using a mixed-method design, data will be mainly collected via surveys among selectors and group interviews with selectors in a lab simulation of a selection meeting where they will collectively select candidates among a list of fictitious candidates. In a truly comparative approach, I will study green parties in three different electoral list systems: Les Verts in Switzerland, Ecolo in Belgium and the Green Party of Aotearoa in New Zealand. My final goal is to uncover whether some profiles of citizens are favored by parties, so if parliaments risk failing to include all categories of the population.