It is now generally agreed that some form of focus on the target code is necessary in adult L2 instruction. One question that remains to be answered is whether all aspects of L2 grammar are equally amenable to pedagogic intervention. A number of researchers have examined the effectiveness of instruction with regard to simple vs. difficult grammar rules. To address this question specifically from the learner's perspective, a questionnaire was administered to two groups of Polish adult learners of English. The first group was asked to assess the difficulty of a number of key areas of English grammar. The second was asked to assess the usefulness of instruction in the same areas. The results indicate that there is a considerable overlap between the judgements of both groups: that is, learners feel they benefit the most from instruction in difficult areas.