The overall aim of the present study is to achieve a better understanding of young instructed Swedish learners’ vocabulary knowledge in L3 French, by examining various aspects of vocabulary depth. Previous research has shown that this learner group’s vocabulary size increases systematically, and at a relatively fast pace, from grade 6 through grade 9 (i.e., from the first year of studies of French and onwards; from age 12 to 15). However, vocabulary size tests only give a quantitative estimation about how many words test takers know, and do not say anything about qualitative aspects of word knowledge. Vocabulary depth, on the other hand, concerns such aspects. In order to arrive at a more complete picture of learners’ word knowledge, both size and depth need to be examined. In the present study, aspects of vocabulary depth were analyzed in learners’ word choices in a written elicited production task. The data consist of 105 written retellings from students in grades 6, 7, 8, and 9. Word choices pertaining to various key elements in the retellings were included in the analysis, with a focus on orthographical, semantic, and morphological aspects of deep word knowledge. The results show that orthographical knowledge is similar throughout the years, with the same spelling difficulties occurring in all the grades at similar rates. Semantic and morphological knowledge seem to develop at a quicker pace, with the 8th and 9th graders having a deeper knowledge of these aspects. It can be concluded that some, but not all, aspects of deep knowledge start to develop during the first four years of studies of French.