The spacing effect is known to be one of the most robust phenomena in experimental psychology, and many attempts have been made to realize effective spaced learning for L2 vocabulary learning. This study compares vocabulary learning with word lists, word cards, and computers in order to identify which material leads to the most superior spaced learning. In the experiment, 226 Japanese high school students studied ten English words with one of the three learning materials: lists, cards, and computers. One-way analysis of covariance (ANCOVA) showed that although no significant difference existed between the Card group and the other two, the PC group significantly outperformed the List group on the delayed post-test. Item analysis using Chi-squares demonstrated that on the delayed post-test, the List group's successful recall rates for four of the ten items were significantly lower than those of the Card or PC group. Correlational analysis indicated that the time invested in learning and the subsequent post-test scores did not correlate significantly for the List and Card groups. Paradoxically, a negative correlation was observed between the PC group's study time and their post-test scores. The lack of meaningful relationships between the study time and subsequent retention may be partially due to the limited ability of certain learners to learn effectively while using certain materials. A questionnaire given to the participants found that, in general, computers were evaluated more favorably than lists or cards. At the same time, however, learners exhibited large variations in their evaluation of computers, implying the importance of considering individual differences when introducing CALL to learners. In summary, the study has demonstrated the superiority of computers over lists, the limited advantage of word cards over lists, and no statistically significant difference between computers and cards. The findings are significant because although the advantages of cards or computers have been advocated, no study has ever tested such claims empirically.