Purpose This study was conducted to compare $^{18}F$-FDG PET/CT and electromyography (EMG) mapping in patients with primary cervical dystonia (PCD) to find dystonic superficial cervical muscles. Methods Ten consecutive patients with PCD (M:F=5:5, age $44{pm}13$ years) whose dystonic posture was not relieved with conventional muscle relaxant therapy were included. Target cervical muscles for the comparison between $^{18}F$-FDG PET/CT and EMG mapping were four representative superficial bilateral cervical muscles: splenius capitis muscle, sternocleidomstoid muscle, upper trapezius muscle, and leavator scapulae muscle. The diagnostic efficacy was compared between $^{18}F$-FDG PET/CT and EMG mapping using physical exam and measurement of rotation angle as the gold standard. Results Among 80 muscles evaluated, there were 21 (26%) dystonic superficial cervical muscles assessed with physical exam and motion analysis. The sensitivity, specificity, and accuracy for localizing dystonic muscles were 76, 92, and 88% for $^{18}F$-FDG PET/CT, and 95, 66, and 74% for EMG mapping, respectively. The sensitivity of EMG mapping was significantly higher than that of $^{18}F$-FDG PET/CT. In contrast, $^{18}F$-FDG PET/CT was significantly superior to EMG mapping for specificity and accuracy. Conclusions $^{18}F$-FDG PET/CT is more specific and accurate than EMG mapping for finding superficial dystonic cervical muscles. The high sensitivity of EMG mapping suggests that $^{18}F$-FDG PET/CT and EMG mapping are complementary for finding dystonic superficial cervical muscles.