This study aims to describe:(1) the dominant type of difficulty, (2) the location of the dominant difficulty, and (3) the factors that cause students have difficulties in solving HOTS-based mathematical problems. This research is descriptive research with mixed methods. Quantitative methods used to find type, and location of student difficulties. Qualitative methods used to find factors that cause student difficulties by interview. The subjects of the research are grade 9th student of junior

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... h school in Kulon Progo with total of 5961 students from 79 schools. The research sample of 371 students are grouped into three categories, namely high, medium, and low, determined by stratified proportional random sampling technique. Data collection are performed using analysis of the results of national standard school examination answers and interviews. Data analysis are performed using a mixed descriptive analysis method that provides an overview about type, location and factors that cause student difficulties. The results of research are as follows. Firstly, the dominant types of grade 9th student difficulties in solving HOTS-based mathematics problems in Kulon Progo are the type of transformation difficulties (66.71%), comprehension difficulties (27.60%), reading difficulties (5.45%), and process skills difficulties (0.24%). Secondly, the dominant location of grade 9th students difficulties in solving HOTS-based mathematics problems for national standard school examination in Kulon Progo are located in determining formula that used to solve the problems (45.24%), 42.06% in determining information that asked, 11.11% in creating mathematics models, and then 0.79% in using mathematics formula or models, and 0.79% in calculate mathematics operation. Thirdly, the factors that cause Junior High School students have difficulties in solving HOTS-based mathematics problems are internal factors (emotional and intellectual) and external factors (teacher's ability in mastering material and family's support especially from parents at school).