The present study investigated whether the teaching of L2 vocabulary with still cartoon pictures and animated cartoon pictures would result in a significant difference in second language learners' receptive and productive knowledge of the target words. Also, the effect of test type (receptive vs. productive) on participants' retention of the target words was examined. Finally, the study tried to find out whether the semantic category of vocabulary words influences the rate of successful vocabulary retention across picture types. For the purpose, a group of 17 ESL students from a Midwestern University participated in both treatments with still and animated pictures, followed by vocabulary tests. The results showed that over 80% of the target words were successfully retrieved on the receptive knowledge tests vs. only about 40% successful retrieval on the productive knowledge tests. Yet, the results did not reveal significant differences in vocabulary gain due to picture type as both treatments showed similar success rate of retention of the target words, especially in view of receptive knowledge. Also, neither of the two types of pictures was effective in facilitating productive knowledge of the target words. In addition, the study found that some semantic categories of vocabulary words may be easier to recall than others.