The Imperfect/Preterite aspectual contrast is one of the most studied topics in Spanish as a second language research. However, there are few works focused on describing the acquisition of modal uses of the Imperfect by L2 speakers. This paper investigates the L1 Russian L2 Spanish speakers' mastery of politeness, evidential and nonfactual modal values of the Imperfect. Based on a Timed Acceptability Judgments Task (TAJT), this study examines the degree of acceptability of Imperfect forms in modal contexts in three groups of advanced level L2 Spanish learners. The results show that only the Imperfect of politeness achieves acceptance rates similar to those of native speakers at the most advanced levels of proficiency. The high degree of lexicalization of some imperfect forms, which function as pragmatic routines in certain communicative situations, is alleged to facilitate this tendency. In contrast, the evidential and nonfactual Imperfect forms present greater challenges for the L2 Spanish speakers. The results of our study indicate that (i) the imperfect forms are not recognized as legitimate alternatives for marking evidentiality and nonfactuality and (ii) reflect a partial form-function mapping of learners' knowledge of the Imperfect and its associated values.