This combined dataset contains the harmonised variables of datasets FSD1260, FSD2269, FSD2653, FSD3067, and FSD3467, which were collected after the Finnish parliamentary elections of 2003, 2007, 2011, 2015, and 2019. The studies belong to the Finnish National Election Studies data series, and their survey data contain Finland's contribution to the international Comparative Study of Electoral Systems (CSES). The harmonised variables, labelled "fnes", comprise responses from one or more collection rounds of the Finnish National Election Studies. Variables from different collection rounds were recoded and combined into the fnes variables at FSD to enable easier comparability between study waves. The data package includes a concordance table (bgF2556.csv) that details which variables in a collection round correspond to each fnes variable. The table also includes a topic and keyword description for the harmonised variables, comparability notes on the variables, as well as SPSS syntax commands and comments relating to the harmonisation of the data. The variables can also be browsed and compared via FSD's Loda portal (https://loda.fsd.tuni.fi/). Out of all the variables in the combined data, approximately 130 were included in all surveys of the series. Additionally, over 200 variables were included in more than one survey. The rest of the variables were specific to individual surveys. Recurring variables in the FNES data included, for example, interest in politics and elections as well as questions about voting and abstaining from voting. The variables also included respondents' political attitudes and views on democracy. A total of 70 different background variables were used over the course of the study series. Some background variables were included in all of the studies, some in fewer and some only in one study. Background variables that were included in all of the studies include gender, economic activity and occupational status, electoral district, level of education, household gross annual income, type of neighbourhood, number of children in the household, number of all persons living in the household, religious affiliation, year of birth, marital status, employment status, mother tongue and language spoken at home.