* Car registration down for the second month in a row
* Registrations down 4 pct to 38,355
* Last year's figure boosted by one-off tax relief
WARSAW, April 3 (Reuters) - Polish new car registrations fell for a second straight month in March, after a 20-month rise, an industry monitor said, with car dealers struggling to match record sales in the same month a year ago, boosted by a one-off tax relief.
Passenger car and small truck registrations fell almost 4 percent last month on a year-on-year basis to 38,355, research institute Samar said on Friday.
In monthly terms, however, registrations rose by 19 percent in March, as dealers competed by offering cars produced in 2014 at discounted prices.
The top-selling car makers in Poland are Volkswagen and its Czech subsidiary Skoda, along with Toyota and General Motors' Opel and Ford . (Reporting by Marcin Goclowski; Editing by David Holmes)