Hidradenitis suppurativa (HS) is a recurrent, debilitating chronic inflammatory skin disease and staging and monitoring of patients with HS have been traditionally based on clinical findings. Recently, the usefulness of ultrasound (US) allows us to better evaluate the severity and to improve the objective follow-up of a patient with HS. A prospective analysis of US examination of HS patients between February 2017 and February 2018 was performed. We report typical two cases of mild to moderate HS. We describe a 23-year-old male with multiple tender oozing nodule on both buttocks and 42-year-old male of multiple erythematous plaque with oozing nodule on both axilla. Two patients conducted sonographic examination at initial visit and follow up visit after 1 month treatment. One patient staged as Hurley stage I and other as Hurley stage II are based on sonographic examination consistent of clinical evaluation and physical examination. US examination at follow up show reduced fluid collection and size reduction at nodule and fistula tract consistent of clinical improvement. Previous reports have demonstrated the effectiveness of ultrasound in HS, but have yet been studied in Korean HS with mild to moderate patients. Sonographic examination in mild to moderate Korean HS could support earlier and more precise management.