Substances like Mamba and Spice can have serious side effects such as paranoia, psychosis and seizures, and have been linked to UK deaths.
Previously known as legal highs, many of the drugs are untested so the risks of taking them is unknown.
There have been a number of cases in towns such as Wrexham, with a lawyer saying there is a "big problem" there.
Crimestoppers is now offering a reward for information on the supply of these drugs.
It wants to hear from people who know of individuals who are manufacturing, importing or supplying these drugs to people in the area, including the homeless.
"These substances are relatively new on the streets, so information is hard to come by as to who is producing and supplying them," said Gary Murray, the charity's north Wales regional manager.
"We understand there is a stigma attached to 'grassing' on people, but these substances are dangerous, to the individuals taking them and to the community around them."
A charity has launched an appeal to help stop the supply of "dangerous drugs" in north Wales.