We have measured the scatter broadening of pulsars in the direction of the
Gum nebula. For the first time. our observations show clear variations of s
cattering properties across the Gum nebula. The IRAS-Vela shell is shown to
be a high scattering region. Our revised estimations of distances to these
pulsars are consistently less bq a factor of 2-3. which has very important
consequences for the deduced values of radio luminosity and tr transverse
velocity of pulsars.