This study investigates Thai EFL students’ attitudes of difficulty towards syntactic structures in English writing and their evaluation of frequencies in using syntactic structures in their writing. The framework of attitudes in this study follows Baker (1992) and Garrett (2010). The methodology of this study uses convenience sampling method. The participants in this study were 30 sophomores, majoring in English from a private university in Thailand. They were asked to fill in a questionnaire concerning syntactic structures in English writing. The instruments in this study were a questionnaire with a five-scale measurement. After the questionnaire was developed, it was validated by three experts. The three experts are PhD instructors in the field of English language and language assessment and evaluation from a renowned public university of Thailand. The descriptive statistical analysis via frequencies and percentages was used to calculate the data analysis. The results in this study show that the participants feel that dependent clauses are difficult for them to use, especially adverbial clauses, reduced adjective clauses and verbless adverbial clauses. Based upon their evaluation toward frequencies of syntactic structures, the participants frequently use existential there constructions and adjective clauses in their writing in English. It is highly expected that the results of this study will be useful for English language teachers to gain better understanding of Thai EFL university students toward their difficulties with syntactic structures in English writing. So, English teachers could bring the results of this study to provide improvement to their students.