A valid cannabis withdrawal syndrome has recently been established, but its clinical importance remains unclear. One method to assess the importance of cannabis withdrawal is to compare it with an established withdrawal syndrome. Cannabis and tobacco withdrawal studies that employed similar methods were used to compare six participant-rated and four observer-rated symptoms. Descriptive and graphic comparisons indicate that the magnitude and time course of withdrawal effects are similar across the two syndromes. These findings are consistent with other evidence supporting the clinical importance of the cannabis withdrawal syndrome. There remains a need for prospective experimental studies to replicate these findings.