1.3mm continuum emission from the
central 4
3
region of the edge-on spiral NGC
4631. About
6/7 of the flux is due to thermal radiation from cool dust and its
distribution has been compared with recent HI and CO maps at similar
angular resolution. The remaining 15% is due to the 
CO(2--1)
line (
), the 
CO(2--1) line (
), and
synchrotron and free-free emission.
Both the CO and 1.3mm continuum are concentrated in the inner 
and have a similar morphology whereas the HI emission is much
more extended. To within observational uncertainties, however, the
dust emission per gram of interstellar matter is similar in the atomic
and molecular components after making the usual assumptions to convert
HI and CO line fluxes to HI and H
column densities.
The fact that the gas mass calculated from the thermal dust emission
is equal to or slightly higher than the mass from the HI and CO lines
suggests that in NGC 4631 the 
ratio
is not overestimated.