The effectiveness of CD-ROM-based English dictionary is compared with conventional printed dictionary for the case of learning a set of English words. When the learners can use dictionary to serch the given words without limit during the fixed learning time, the test scores of learners using CD-ROM-based dictionary were apparently higher than those of learners using printed dictionary. In the contract, when learners were allowed to consult dictionary only one time each for given word. no significant difference between the test scores was detected, while the learning time of using CD-ROM-base dictionary was shorter than that of using printed dictionary.