OBJECTIVE: To confirm the clinical utility of diaphragmatic needle electromyography (EMG) in patients with respiratory dysfunction. METHOD: Needle electorode was inserted into the muscle just above the lower costal margin between anterior axillary and medial clavicular lines. Case 1 who showed no response bilaterally in a phrenic NCS and a complete denervation of the diaphragm on needle EMG was unable to be weaned off from the ventilator. Case 2 who showed normal electrodiagnostic findings was successfully weaned off from the ventilator. Case 3 who showed a respiratory insufficiency from organophosphate intoxication had normal electrodiagnostic findings and was able to be successfully weaned off from the ventilator with a psychiatric support. RESULT: We ruled out the possibility of lack in central respiratory drive and weaned off patients from the ventilator, based on a normal firing pattern of motor unit potentials. CONCLUSION: Phrenic nerve conduction study (NCS) alone is not sufficient to find out the nature of respiratory dysfunction. Needle EMG of the diaphragm can be helpful in determining the pathogenesis, but its utility has been limited due to its potential risks. However we have confirmed that the needle EMG of diaphragm is a safe and easy study to perform and can provide a valuable information in the evaluation and management of respiratory dysfunction.