Gordon Clement found four pounds of pot inside the picture frame of a painting he bought about five years ago.
The 80-year-old Georgia man got the painting of flowers in a vase at a post office auction.
He discovered the pot stash when he tried to sell the painting last weekend at another auction.
Clement told his lawyer about the secret of his artwork and turned it over to authorities.
Clement says he was going to ask 25 bucks for his picture.
Police say the pot was worth about $4,800.