The number of cannabis users increased up to 188 million users worldwide in 2017. Smoking and vaping are the most common consumption routes with formation of side-stream smoke/vapor and secondhand exposure to cannabinoids has been described in the literature. External contamination of hair by cannabis smoke has been studied but there are no studies on third-hand cannabis exposure due to deposition of smoke or vapor on surfaces. We tested whether cannabinoids could be detected on surfaces and objects in a room where cannabis is vaporized. Surface samples were collected using isopropanol imbued non-woven wipes from hard surfaces and objects. Each surface was swabbed three times with standardized swabbing protocol including three different patterns. Samples were analyzed using LC-ESI-MS/MS in combination with online extraction. THC was detected on 6 samples out of the 15 collected in the study room at quantifiable levels ranging 348-4882 ng/m2. Negative control samples collected from areas outside the study room were all negative. We demonstrated that surfaces exposed to side-stream cannabis vapor are positive for THC at quantifiable levels. This study represents a first step in understanding how side-stream cannabis vapor deposits in the environment and potentially results in a tertiary exposure for users and non-users.