How can I do conditional 'drop table' in Postgres

if exists (select * from sysobjects where id =
object_id(N'[dbo].[pp_fisk]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
drop table [dbo].[pp_fisk]
GO

For instance, this is a valid script in Ms SQL, it will drop table
pp_fisk only if it exists, is there a way to do something similar in
Postgres? Tnx in advance.

Dragan