  The measurement of proper motions in CSOs is a powerful tool to determine the
dynamical evolution of the newly born extragalactic radio sources. We observed
3 CSOs with the VLBA in 2004 and in 2006 to monitor changes in their structure
and measure the separation velocity of the hot spots. It is important to
increase the size of the samples of CSOs with measured expansion velocity to
test the existance of frustrated objects, and put stringent constraints on the
current models. We found for all the three objects observed a transverse motion
of the hotspots, and we suggest as the more likey explanation a precession in
the jet axis. This behaviour likely inhibits or at least slows down the radio
source growth because the head of the hotspot continuously hits new regions of
the ISM. Therefore these radio sources may represent an old population of
GPS/CSOs.
