  We present a systematic analysis of all the BeppoSAX data of the soft
gamma-ray repeater SGR 1900+14: these observations allowed us to study the long
term properties of the source quiescent emission. In the observation carried
out before the 1998 giant flare the spectrum in the 0.8-10 keV energy range was
harder and there was evidence for a 20-150 keV emission, possibly associated
with SGR 1900+14. This possible hard tail, if compared with the recent INTEGRAL
detection of SGR 1900+14, has a harder spectrum (power-law photon index ~1.6
versus ~3) and a 20-100 keV flux ~4 times larger. In the last BeppoSAX
observation (April 2002), while the source was entering the long quiescent
period that lasted until 2006, the 2-10 keV flux was ~25% below the historical
level. We also studied in detail the spectral evolution during the 2001 flare
afterglow. This was characterized by a softening that can be interpreted in
terms of a cooling blackbody-like component.
