Purpose of Review <p>This review focuses on the diagnosis and management of disorders of water imbalance in children, including the syndrome of inappropriate antidiuresis [SIAD, previously called syndrome of inappropriate antidiuretic hormone secretion (SIADH), arginine vasopressin deficiency (AVP-D, formerly central diabetes insipidus), and arginine vasopressin resistance (AVP-R, formerly known as nephrogenic diabetes insipidus). We highlight contemporary approaches for subspecialist care.</p> Recent Findings <p>Emerging tools, such as stimulated copeptin levels, have the potential to improve diagnostic accuracy and decrease reliance on more burdensome tests. Novel therapies such as vasopressin receptor antagonists have demonstrated efficacy in management of SIAD, though pediatric use remains limited. For AVP-D, potential newer formulations such as sublingual desmopressin may offer practical advantages in pediatric patients, while in AVP-R, promising therapies include pharmacologic chaperones and bypass therapies that are under investigation and may expand future treatment options.</p> Summary <p>Disorders of water imbalance in pediatrics require careful diagnostic workup and individualized therapy. A case-specific approach, tailored to the clinical context is essential to optimize patient outcomes.</p>