Abstract The following study is about some of the factors that influence a correct using of the subjunctive mood and what type of clauses with subjunctive that Swedish students at university level find the hardest. The aim of this essay is to investigate some of the factors that affect the application of the subjunctive mood. This study also attempts to show a tendency of what kind of sentences that Swedish students have most problems with. This study is carried out with 97 students from three Swedish universities. They have all studied Spanish between six months and one year and a half at university level. This investigation contains a questionnaire in two parts. The first part is constructed with general questions about the ability of the informants regarding the subjunctive mood and the second part contains a test of knowledge of this grammatical phenomenon. The informants had to choose between verbs in the indicative or the subjunctive mood. The answers of this questionnaire were used to find out which factors were of greatest importance for the application of the subjunctive. With the help of the questionnaire, the most difficult clauses with subjunctive from the test could be distinguished. The results of the investigation show that the most significant factor that influences on the application of the subjunctive mood is the student’s own estimation of the ability to write Spanish. It was also clear that the subjunctive clauses formed by time conjunctions were considered the hardest ones by the students.   Keywords: Grammar, mood, subjunctive, factors, clauses with subjunctivePalabras clave: Gramática, modo, subjuntivo, factores, cláusulas construidas con el subjuntivo