Periodic Mesoporous Organosilicas (PMOs) emerged on the scene of Materials Chemistry in 1999. Since then, the literature concerning their synthesis, characterization and applications has rapidly grown. From the very beginning, one of their main applications has been for heterogeneous catalysis. In order to impart them a catalytic behaviour, they have been functionalized to create catalytic sites on their pore walls, sometimes following well-established strategies reminiscent from mesoporous silicas but other times carrying out new methods based on the existence of organic bridges in their framework. Herein, we will give an overview on their use as catalysts, but being focused on the properties that distinguish them from mesoporous silicas and on those processes where their application involves a real advantage over other materials.