The present invention relates to bi- and tricyclic compounds of the general formula (I) (I) wherein the dashed lines independently of each other represent a single or a double bond, X represents a group of the formulae X1 to X3 wherein the asterisk denotes the point of attachment to the rest of the molecule, R1a and R1b, independently of each other, are selected from hydrogen or methyl, or R1a together with R1b with R form a methylene or ethylene group, R2, R3a, R3b, R4, R5a and R5b, independently of each other, are selected from hydrogen or methyl, R6 is selected from hydrogen, methyl or ethyl, and R7 is methyl or ethyl, to a method of preparing said compounds, to the use of a bi- or tricyclic compounds or of mixtures of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof as aroma chemicals; to the use of a bi- or tricyclic compound for modifying the scent character of a fragranced composition; to an aroma chemical composition containing a bi- or tricyclic compound or a mixture of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof; and to a method of preparing a fragranced composition or for modifying the scent character of a fragranced composition, comprising incorporating a bi- or tricyclic compound or a mixture of two or more bi- and tricyclic compounds or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof into said composition.