Given the presence of a variety of political conditions, Portugal provides an excellent opportunity to understand which factors could affect the opposition’s behaviour and determine its conduct in parliament. First, it permits us to test the effect of a systemic variable traditionally thought to affect the opposition’s behaviour, namely the executive’s type. Portugal, in fact, has experienced the alternation of majority and minority governments, which implies very different political opportunities for the opposition parties. Second, it allows us to test the difference in the behaviour of temporary and permanent opposition (at least until the 2015 election), given the presence of two mainstream parties alternating in office – the Socialist Party and the Social Democrats – and three radical left parties – the Portuguese Communist Party, the Greens and the Left Bloc – always in opposition. Finally, in recent years, it offers an insight into the impact of the economic crisis on government-opposition dynamics. We will explore the impact of the three abovementioned factors by investigating the opposition’s behaviour in Portugal in five legislative terms, namely during the three governments led by the Socialist Party (2005–2011) and the two led by the centre right coalition composed of the Social Democrats and the conservative People’s Party.