High sensitivity 21-cm HI line observations with an rms noise level of ~0.5mJy were made of 35 spiral galaxies in the Coma Supercluster, using the refurbished Arecibo telescope, leading to detection of 25 objects. These data, combined with the measurements available in the literature, provide the set of HI data for 94% of all late-type galaxies in the Coma Supercluster with an apparent photographic magnitude m_p_<=15.7mag. We confirm that the typical scale of HI deficiency around the Coma cluster is 2Mpc, i.e. one virial radius. Comparing the HI mass function (HIMF) of cluster with non-cluster members of the Coma Supercluster we detected a shortage of high HI mass galaxies among cluster members that can be attributed to the pattern of HI deficiency found in rich clusters.