Omeprazole is usually administered as encapsulated enteric-coated granules and enteric-coated tablets because of its acid-labile nature. For children and patients who can not swallow, it can be mixed with water or other liquid after a capsule is opened or a tablet is crushed. This study was performed to compare omeprazole liquid formulations of tablet and capsule Omeprazole 20 mg capsule containing enteric coated granules was opened and 20 mg entric-coated tablet was ground to be mixed with sodium bicarbonate solution, orange juice or water. Each liquid formulation was poured into dissolution tester, mixed with first solution (artificial gastric juice; pH 1.2) for two hours, then with second solution (artifical enteric juice; pH 6.8) for thirty minutes. pH was measured periodically for two and half hours. Samples were drawn periodically, mixed with lansoprazole as an internal standard, and injected to HPLC. As results, pH of sodium bicarbonate solution of omeprazole was significantly higher than that of orange juice or water in first solution (6.2-7.4 vs. 1.2, p<0.005). At 150 min, concentrations of omeprazole in three diluents with granules and in sodium bicarbonate solution of tablet powder sustained significantly higher than in other solution of tablet powder (p<0.001). In conclusion, enteric-coated granules from capsule with three diluents and powder from tablet in sodium bicarbonate solution was stable during dissolution test, which would be appropriate and recommended for patient who can not swallow solid preparations.