Justin Bieber had drugs and drug paraphernalia strewn all over his house when it was raided Tuesday ... but drugs were not on deputies' radar ... TMZ has learned.

Sources familiar with the situation tell TMZ ... when L.A. County Sheriff's deputies searched the house ... there were 2 large cookie jars filled with weed in plain view. There were also 4 - 5 empty codeine bottles in the mansion.

There were also 3 bongs -- 1 in the TV room and 2 in the kitchen.

There were styrofoam cups scattered throughout the house that had elaborate drawings on them ... including the names of the people who used them. The cups, we're told, were used for Sizzurp (also called lean) -- which is Justin's drug of choice. We're told he likes to draw on the cups with markers after using them.

And speaking of Sizzurp ... Sprite is usually part of the mix, but we're told Justin preferred pineapple Fanta instead. There were empty Fanta bottles that were discolored ... we're told from the codeine.

There were lots of "swisher sweets" cigars laying around the house -- Bieber's preferred way to smoke marijuana.