Overactive bladder which is defined by symptoms of urinary frequency and urgency but cannot be defined by pathogenesis of this condition, can be considered as a representative of storage failure. Dysfunctional voiding which is caused by dyssynergia of the detrusor and urethral sphincter is the most common form of emptying failure. Through inadequate relaxation of urethral sphincter during contraction of detrusor muscle for voiding, intravesical pressure increases and eventually results in pathologic changes of the bladder. However, overactive bladder which is a failure of storage and dysfunctional voiding which is a failure of emptying are not completely different diseases, but are closely related and can be switched from one type to the other. Continuously increased intravesical pressure by abnormal contraction of the external urethral sphincter and primary or secondary involuntary detrusor activity are the major components in the pathophysiology, Thus thorough evaluation of the bladder and urethra and treatment of UTI and constipation which can affect the function of the bladder and urethra must be considered when establishing a treatment. If behavioral problem is accompanied or the patient shows poor compliance to urotherapy, psychological intervention by a specialist can be helpful. With increasing interest in the quality of life, active basic research in the field of voiding dysfunction and development of new drugs are in progress and shows a promising future. Meanwhile, pediatric urologist must strictly assess the significance of this disease entity during childhood through long term follow up of these children into adulthood.