  The class of Compact Steep-spectrum Sources is dominated by double-lobed
objects (70%). The remaining 30% are jet-dominated objects, with the jet
brightened either by Doppler boosting or by interaction with the ambient media.
We show that there is both observational and statistical evidence in favour of
an interaction between jets and dense gas clouds. Such an interaction should
happen in the Narrow Line Regions. The images of four CSSs observed by us with
VLBI are also presented. These sources do show large bent jets in the first kpc
from the nucleus.
