Check this out.

Breston (pictured police dog) uncovered a shipment of marijuana in heat-sealed Mylar bags, inside plastic-lined crates sealed with foam sealant, inside a closed storage garage.

Howstuffworks "How Police Dogs Work"

Damn! But then again, they say a dog's sense of smell is like 1000x greater then ours... so there ya go. The cops just train them so that they get a treat or a reward whenever they can point to a specific location where they smell it from.

I should train my dog to do that. That way instead of trying to find a dealer I could just take the pooch for a walk and whenever he alerts on someone just be like, "what's up man... got a quarter?"