Cannabis contains a wide range of terpenes and terpenoids that are mainly responsible for their distinctive aroma and flavor. These compounds have also demonstrated therapeutic effects either alone and/or as synergistic compounds with other terpenes, terpenoids, and/or cannabinoids. Several studies have attempted to fully characterize terpenes and terpenoids in cannabis; however, most of these studies used one-dimensional gas chromatography, which often results in the co-elution of the compounds. In the present study, we analyzed terpenes and terpenoids in the dried flowers of six cannabis strains using a two-dimensional gas chromatograph time-of-flight mass spectrometer (GC × GC-TOFMS). A total of 146 terpenes and terpenoids were detected across all six cannabis strains with an enhanced separation of 16 terpenes and terpenoids in the second dimension. Additionally, we achieved enhanced separation of four terpenes and terpenoids from a standard mixture in the second dimension. Chemical differences were observed in the number and relative abundance of monoterpenes, monoterpenoids, sesquiterpenes, and sesquiterpenoids in all six strains. We were also able to identify four new terpenoids in cannabis, which are reported here for the first time.