The relations between immigrants and host society members are inherently affected by dynamics of similarity and dissimilarity. Do host society members react more positively to immigrants who are similar or who are dissimilar? This was the question driving this work. Having as background the Portuguese context, this work analysed the attitudes of Portuguese citizens towards (similar and dissimilar) immigrant groups. Results show that this phenomenon is far from straightforward depending on several factors, namely the dimensions to which this similarity and dissimilarity refer to.