Recent evidence indicates that currently accepted mass-loss rates may need to be revised downwards when small-scale density inhomogeneities (clumping) are taken into account. Only a consistent treatment of ALL possible diagnostics from the UV through radio, scanning different regions of the stellar wind, and analyzed by means of state of the art model atmospheres, will allow to determine the true mass-loss rates. To this end we have assembled a variety of multi-wavelength data for a carefully selected sample of 28 O4-B8 stars. However, one crucial observational set was missing: far-IR diagnostics of free-free emission, which uniquely constrain the clumping properties of the wind at intermediate regions. We have used Herschel/PACS photometric mode to fill this crucial gap, studying the 70 and 100 micron fluxes. Here, we present preliminary photometric Herschel/PACS flux measurements of our sample as well as a first detailed analyses for some of the sources.