  We have analysed a series of Suzaku data and one dataset of XMM-Newton of the
SU UMa type dwarf nova VW Hyi in optical quiescence. The observed spectra in
the 0.2-10 keV band are moderately well represented by multi-temperature
thermal plasma emission models with a maximum temperature of 5-9 keV and
bolometric luminosity of 2.4-5.2 $\times$ 10$^{30}$ erg s$^{-1}$. The mass
accretion rate derived from the hard X-ray spectra does not show any clear
trend as a function of time since the last superoutburst, in contradiction to
theoretical predictions of the disc behaviour of a SU UMa type dwarf nova. The
mass accretion rate, on the other hand, shows a clear declining trend with time
since the last outburst (including the superoutburst). The rate of decline is
of the same order as that evaluated from the hard X-ray light curves of the
other two dwarf novae SS Cyg and SU UMa. The standard disc instability model,
on the other hand, predicts that the mass accretion rate should increase
throughout the optically-quiescent phase. We need further observation and
theoretical consideration to resolve this discrepancy.
