Pediatricians often see babies in the clinic for neck masses, which are basically enlarged lymph nodes. In children, the lymphatic system is well developed and there are many lymph nodes in the neck, and swollen lymph nodes can be palpated under the jaw, in front of the ear, behind the ear and in the occipital area. After puberty, the lymph nodes gradually shrink with age, and the swollen lymph nodes in the neck are divided into infectious and non-infectious ones. Reactive lymphadenitis secondary to a viral infection is the most common cause of swollen lymph nodes in the neck. It usually appears with upper respiratory tract infections, pharyngitis, tonsillitis, otitis media, mouth ulcers, and dental disease. The lymph nodes are bilaterally swollen, soft, well-mobile, and may be painful to pressure. The swollen lymph nodes may resolve spontaneously with the improvement of the infection. If the neck is swollen, pain is pronounced, and neck movement is limited with fever, acute bacterial lymphadenitis or purulent lymphadenitis is considered and requires treatment with sensitive antibiotics. Some subacute and chronic lymphadenitis are associated with tuberculosis infection and cat-scratch disease. Non-infected lymph node enlargement is seen in malignant tumors, connective tissue diseases such as leukemia, lymphoma, Kawasaki disease, idiopathic arthritis, and systemic lupus erythematosus. If the lymph nodes are persistently enlarged, with inconspicuous pressure pain and unclear borders, or accompanied by fever, hepatosplenomegaly, or rash, malignant lymphoma or connective tissue disease cannot be excluded and need to be examined by a physician. Enlarged lymph nodes in the neck are a common symptom in children, and the etiology ranges from benign to malignant, covering a wide range of diseases. In children, most are reactive lymph node enlargement. However, if there is a painless progressive swelling of the lymph nodes, or if it is accompanied by fever or rash, it needs to be taken seriously.