The Finnish National Election Study of 2003 revealed that most voters in Finland do not identify with parties and are self-described as independents. In this article it is asserted that partisan attachments affect Finnish parties' optimal positions despite the large amount of independents. To show this, the article is divided in two parts. In the first part, voters' decisions are assumed to be deterministic. To show the effect of party identification under deterministic voting, two different types of simulations are conducted: the partisan type, where the partisans' voting behaviour depends on their distance from the party and on a degree of partisan attachment, and the apartisan type, where voting behaviour depends solely on policy issue distance. Results show that partisan attachments drive parties to adopt different ‘one-off’ optimal positions than they would if party competition was solely based on policy issue distance. In the second part of the article, it is assumed that voters' decisions are probabilistic. Upon showing that party identification makes a voting model solely based on distance significantly more fit, the predicted probabilities of party choice are computed. Results indicate that the probability that a voter will vote for a party is higher when the party is located at its optimal position according to the partisan type of simulations rather than the apartisan one.