  We have observed the HI distribution in an area 40' x 40' around the neutron
star candidate RX J0822-4300, which is located in the supernova remnant Puppis
A. The observations of the 21 cm line were obtained with the Australia
Telescope Compact Array (ATCA) and were combined with single dish data from the
Southern Galactic Plane Survey. The spatial resolution is 90", and the velocity
resolution, 1 km/s . A sensitivity of ~ 0.7 K was achieved. The results
revealed a double lobed feature of reduced emission at +16 km/s, centered on
the central compact object (CCO), and aligned with an HI hole blueshifted by 13
km/s. The HI depressions have probably been created by the sweeping up of ~ 2
solar masses. The alignement between the lobes and the optical expansion centre
of Puppis A suggests that the CCO could be ejecting two opposite jets. The
velocity at which the two lobes are best defined allowed us to confirm that the
distance to Puppis A is 2.2 kpc, based on a systemic velocity of +16 km/s. The
hydrogen column density computed using this systemic velocity is consistent
with estimates from models for X-ray spectra, thus reinforcing our conclusion
that the kinematic distance is 2.2 k pc.
