This study investigates language productivity in a foreign language learner output obtained via two different modes of computer-mediated communication (CMC): asynchronous (email dialog journals) and synchronous (chatroom sessions). The research questions to be answered in the study were: (a) Which form of CMC, synchronous (chatroom activities) or asynchronous (email), would be more effective in increasing language productivity in foreign language learning? And (b) Which form of CMC would participants prefer? A within-subject design was used in the study with 24 participants who were studying first semester Spanish with one instructor. Participants emailed a dialog journal in Spanish to their instructor every Tuesday during the semester and they also attended the chatroom every Thursday to chat with their instructor and with each other in Spanish. Students met in the conventional classroom three times a week and via CMC on Tuesdays and Thursdays. The researcher tallied how many new vocabulary words participants produced in the email journals as opposed to new vocabulary words produced in chatroom sessions. (The researcher counted only those words that did not appear in the textbook or had been taught in class.) Results showed that there were no significant differences between the two CMC modes. However, a higher number of words were produced in the chatroom discussions than in the email messages. Fifty percent of the students preferred electronic mail and the other 50% were more inclined towards chatroom sessions. The author concluded that both techniques had benefits for vocabulary enrichment and productivity and that both tools enhanced the language acquisition process.