Abstract A fundamental task for reasoning with preferences is the following: given input preference information from a user, and outcomes α and β, should we infer that the user will prefer α to β? For CP-nets and related comparative preference formalisms, inferring a preference of α over β using the standard defifinition of derived preference appears to be extremely hard, and has been proved to be PSPACEcomplete in general for CP-nets. Such inference is also rather conservative, only making the assumption of transitivity. This paper defifines a less conservative approach to inference which can be applied for very general forms of input. It is shown to be effificient for expressive comparative preference languages, allowing comparisons between arbitrary partial tuples (including complete assignments), and with the preferences being ceteris paribus or not