I will report on our recent study aimed at detecting molecular gas in the main body and in the tails of a sample of 5 jellyfish galaxies that have been observed within our ongoing MUSE Large Program (GASP). The analyzed sample is constituted by the most extreme jellyfish galaxies, for which the analysis of the ionized gas has already demonstrated that the mechanism at play in regulating 5the gas outflow is the ram pressure stripping. The detection of molecular gas in the tails and the broad characterization that we have been able to extract with APEX data is one of the key ingredients to understand if and how the molecular gas is subject to the same physical process.