  We present 12CO (2-1) data of three Virgo spirals - NGC 4330, NGC 4402 and
NGC 4522 obtained using the Submillimeter Array. These three galaxies show
clear evidence of ram pressure stripping due to the cluster medium as found in
previous HI imaging studies. Using high-resolution CO data, we investigate how
the properties of the inner molecular gas disc change while a galaxy is
undergoing HI stripping in the cluster. At given sensitivity limits, we do not
find any clear signs of molecular gas stripping. However, both its morphology
and kinematics appear to be quite disturbed as those of HI. Morphological
peculiarities present in the molecular and atomic gas are closely related with
each other, suggesting that molecular gas can be also affected by strong ICM
pressure even if it is not stripped. CO is found to be modestly enhanced along
the upstream sides in these galaxies, which may change the local star formation
activity in the disc. Indeed, the distribution of H$\alpha$ emission, a tracer
of recent star formation, well coincides with that of the molecular gas,
revealing enhancements near the local CO peak or along the CO compression. FUV
and H$\alpha$ share some properties in common, but FUV is always more extended
than CO/H$\alpha$ in the three galaxies, implying that the star-forming disc is
rapidly shrinking as the molecular gas properties have changed. We discuss how
ICM pressure affects dense molecular gas and hence star formation properties
while diffuse atomic gas is being removed from a galaxy.
