Brachial cleft cyst is a congenital anomaly arising from persistent elements of branchial apparatus. It may assume the form of cyst, sinus or fistula and constitutes 30% of all congenital anomalies of the neck region. Brachial cleft cyst is usually recognized in patients before the 5th year of age, but it may appear in patients between 20 and 40, when it enlarges owing to infection. It reveals then as a smooth, resilient tumor in lateral region of the neck. Ultrasonography, computerized tomography and magnetic resonance may be used to evaluate and differentiate these lesions as well as to reveal the presence of fistula, which is important to plan the proper surgical treatment. The only effective treatment is total surgical excision. The lack of treatment puts a patient at risk of infections, while incomplete removal might result in recurrence.