A DOPEY scheme to give away drugs has left NSW police in possession of three garbage bags stuffed full of cannabis.

The haul, weighing in at 16 kilograms, was found on the side of a road in Bomaderry, about 160 kilometres south of Sydney.

Adorning the haul were cardboard signs emblazoned with the spraypainted message, "Free dope. Smoke. Mull up."

A passerby found the cannabis about 10am last Saturday and, upon closer inspection, discovered freshly harvest marijuana leaves inside.

Police say they don't expect the owners will come forward, and the drugs will be destroyed.