Police seized 4.8 tonnes of synthetic drugs worth around PLN 193 million (EUR 42.3 mln) in raids on production laboratories in the west, south-east and north Poland.
Six persons have been arrested in the raids, which took place on Tuesday. In all 13 persons are suspects in the case.
Police in northern Poland also raided a depot where the narcotics were being stored pending sale.
The drugs include marijuana, clephedrone, mephedrone, amphetamine, cocaine and MDMA pills.
Police do not exclude further arrests in the case.