Background and Objectives: This study aimed to examine factors of poor outcome by analyzing the outcomes of bilateral subthalamic deep brain stimulation in Parkinson's disease after 3 years. Methods: We assumed that patients who could not manage independent life in their best stimulationon/ medication-on condition after a defined period might not have been a good surgical candidate. A poor outcome is defined as a failure to maintain functional independence at three years during a stimulation-on/medication-on state. Results: A total of 84 patients underwent bilateral subthalamic deep brain stimulation and all were followed up for 3 years. We excluded one patient who had intracranial hemorrhage. Twenty-one patients of the 83 patients could not keep up independent life even during their best condition for the following reasons: freezing in 15 patients, dementia in 5, depression in 3, musculoskeletal problems in 7, and cancer in one patient. Conclusions: Many patients could not keep up independent life during their best condition as early as three years after deep brain stimulation. Musculoskeletal problems were one major cause of disabilities, as were freezing and dementia. We emphasize that musculoskeletal problems need more attention in the preoperative screening of deep brain stimulation candidates and during the follow up.