Plagiarism as a topic of research in the university context has not ceased to be a constant concern due to its multiple repercussions. This paper describes the process followed in the validation of the Questionnaire of attributions for the detection of coincidences in academic works (CUDECO), whose purpose is to evaluate the relevance that to cite correctly and to detect the causes that lead to commit plagiarism. From a sample of 2,331 students, an analysis of reliability as internal consistency and an exploratory factorial analysis (AFE) of the instrument is carried out. The analysis of reliability leads to propose a readjustment in the questionnaire initially designed. The factorial study suggests a structure configured by five factors: concept of plagiarism and its types (partial and total), causes that motivate the commission of it both internal (specific to the subject) and external (outside the subject) and the attitudes of the peer group towards plagiarism, findings in the line of research previous