Significant spaces

PostGreSQL 7.2.4

Can anyone tell me where trailing spaces are significant in CHAR, VARCHAR and TEXT fields?

We pass a VARCHAR variable into a 3rd party language product 'function' as a CHAR(250). The CHAR(250) field is then used to interrogate a table to see if that value exists. If not, a row with that value is inserted into the table as a VARCHAR(N). The issue is that the value when inserted into the VARCHAR in the table appears to carry trailing spaces, so when a subsequent lookup is performed with the same value, the value is not 'found' and a further insert occurs.
The problem appears to disappear if I change the definition of the passed parameter to a VARCHAR as well.
Is this a known issue?

Regards, Steve Tucknott ReTSol Ltd DDI: 01903 828769