The balloon-borne submillimeter instrument PRONAOS has
observed one square degree areas towards the Orion and M 17 molecular
clouds. The 2'-3.5' resolution
maps obtained in four wide wavelength bands between 200 μm and 600 μm, exhibit the dust distribution in these regions. We analyze the temperature and
spectral index of the dust, and we show the anticorrelation between these two
parameters. We derive estimations of the ISM column densities and masses in these regions.