The purpose of this study is to examine the cognitive processes underlying the listening comprehension section of IELTS and to investigate if they vary in terms of difficulty. For this purpose, a checklist of possible cognitive operations was prepared based on the literature and the candidates’ feedback. The checklist consisted of six cognitive operations. A sample of IELTS listening test was given to 310 upper intermediate and advanced students of English. Linear logistic test model was employed to analyse the data. Findings showed that keeping up with the pace of the speaker and understanding reduced forms were the most difficult operations for the listeners. Altogether, the six operations explained 72% of the variance in item difficulty estimates. Implications of the study for the testing and teaching of listening comprehension are discussed.