This thesis investigates learners’ reading practices and especially the processing of cross-linguistic similarities at the lexical level. The aim is to determine how learners proceed in order to understand text in French (L3). Data were collected using various reading comprehension tasks in combination with the think-aloud method. Reading comprehension was mainly assessed through a translation task while the reading practices were observed in think-aloud protocols. According to a reading comprehension score, 20 learners were divided into high level and low level groups. The majority of participants were Swedish learners who are also proficient in English L2. Another group of 10 Swedish learners and 10 French native speakers participated in a cross-linguistic word association task. Reading practices were defined as including skills, strategies and readers’ reactions to the text, the tasks and their own capacities. A typology of twelve reading practices was established including three categories based on intralingual and interlingual similarities. Results from the translation task and the think-aloud protocols show that interlingual processing is more important when learners have difficulties in understanding text content. The more learners in the low level groups relied on intralingual and especially interlingual similarities the less they understood the text content. The high level groups on the other hand used reading practices such as reformulation or translation procedures. The think-aloud protocols also show that learners believe that they compare words in the French text (L3) with English similar words (L2) although their interlingual processing during translation actually confirms the dominance of Swedish (L1). Moreover, results from a cross-linguistic word association task suggest that French Swedish/English cognates and false friends activate this type of words more often than French control words. Cross-linguistic stimuli actually triggered patterns of potential interlingual similarities, for example sacrifice (stimulus) – religion (response), even more than words that are similar to the stimulus diplomate – diplom ‘diploma’.