Sometimes referred to as blotter art or trips, the paper squares contain the drug 25i NBOH and are usually sold as acid or LSD.
Officers said the effects can be "strong, unpredictable and overwhelming".
A Police Scotland spokeswoman said: "Police Scotland recently seized a quantity of Class A Hallucinogenic drug in Paisley which was in the form of small paper squares, often referred to as blotter art, and may be being sold locally or elsewhere in Scotland.
"There are often different substances being sold in a similar fashion which make it impossible to visually identify what drug or what strength of drug is being sold," she said.
The spokeswoman warned that the paper squares are likely to be sold as other drugs. "However, the effects of this hallucinogenic can be strong, unpredictable and can be overwhelming to the user," she added.
"With the festival season now upon us the temptation can be there for people to use substances of this type and a similar drug elsewhere in the UK resulted in people requiring hospital treatment.
"Our message is clear in that substance use of this type is inherently dangerous, particularly when taken with other substances including alcohol. It is illegal and could have serious consequences. If you or anyone you are with has taken illicit substances and becomes unwell we urge you to seek appropriate medical attention."
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