Opposition parties are normally exposed to two contrasting pressures. One comes from the need to mark their position as distinct from that of the government and is a pressure towards conflict; the other is a pressure towards cooperation and comes from the wish to take part in the decision-making and influence policy decisions. Given the recent transformations in the party context and the “growing divide” in European party systems between parties which claim to represent but usually do not govern, and those that govern but are no longer seen to represent (Mair 2011), this panel aims to explore the behaviour of two possible types of opposition: one carried out by the mainstream parties – i.e., those parties with government aspirations and a legitimate expectation to be called to replace the government in the near future – and that of parties permanently excluded from power – usually the more radical. Is the behaviour of these two types of parties actually different, once in opposition? Can we distinguish between two modes of opposition according to their parliamentary behaviour and strategy? Has any change been observed since the outbreak of the economic crisis? This panel will attempt to answer these questions, thanks to the contribution of scholars investigating the behaviour of parliamentary opposition in EU member states in recent years.