The circular dichroism (CD) and circular dichroism of anisotropic samples (ACD) of cisoid enones 3-methyl-3 alpha,5 alpha-3,3＇,4＇,5＇-tetrahydrobenzo[2,3]cholest-2-en-1-one (4) and its 3 beta-diastereoisomer 7 have been investigated. The relation between structures, obtained from energy minimization and from X-ray analysis, and the signs of the Cotton effects (CEs) is discussed in terms of previously published rules.(1,2) A modification of recently published rules connecting signs of the n pi* and band II CEs with enone chirality is postulated. The ACD results allow an interpretation of the breakdown of the helicity rule for the n pi* band of 7 as a consequence of a different variation of the different coordinates Delta epsilon(ii)* in Delta epsilon = (Delta epsilon(11)* + Delta epsilon(22)* + Delta epsilon(33)*)/3 by vibronic coupling in comparison to the coordinates Delta epsilon(ii)* of 4. This change of the size of the Delta epsilon(ii)* of 7 originates from a different perturbation of the enone chromophore by the cyclohexene A＇ ring which causes a non-symmetrically deformed A ring system in 7 (non-symmetrical boat conformation) compared with the slightly distorted symmetrical chair conformation in 4.