Since they promote separation from national frameworks, independentist parties are easily labelled as anti-system parties. This contribution shows how a study of party dynamics in three Western Mediterranean island jurisdictions (Sardinia, Balearic Islands, and Corsica) leads to a rather different conceptualisation of their nature and influence. Political parties favouring independence are still likely to influence other political parties and the political system as a whole. They do so mainly by adopting various, often ambiguous, accommodative strategies, which relate to their difficulty in attaining and/or maintaining a significant party status and electoral presence. Above all, the independentist parties' influence is highly variable, especially in relation to their closest rivals, and can only be evaluated by taking into consideration external factors, such as state organisation. Thus, one needs to examine the independentist parties' political interactions and influence on policies, and not just their teleological and ideological positioning.