  The Two Micron All Sky Survey, along with the Stellar Population Synthesis
Model of the Galaxy, developed in Besancon, is used to calculate the extinction
distribution along different lines of sight. By combining many lines of sight,
the large scale distribution of interstellar material can be deduced. The
Galaxy model is used to provide the intrinsic colour of stars and their
probable distances, so that the near infrared colour excess, and hence the
extinction, may be calculated and its distance evaluated. Such a technique is
dependent on the model used, however we are able to show that moderate changes
in the model parameters result in insignificant changes in the predicted
extinction. This technique has now been applied to over 64000 lines of sight,
each separated by 15 arcmin, in the inner Galaxy (|l|<=100 deg, |b|<=10 deg).
Using our extinction map, we have derived the main characteristics of the large
scale structure of the dust distribution: scale height and warp of the ISM disc
as well as the angle of the dust in the Galactic Bar. This resulting extinction
map will be useful for studies of the inner Galaxy and its stellar populations.
