both HMO and PPO are managed health care system. With HMO's you can only choose a physician from the HMO's member physicians.They only provide general medical care, and if you need to see a specialist, you need to be referred to him by your primary physician, and in some instances you might need to consult HMO.Also they do not provide coverage for care received from doctors who are not in their network.the But you do not have to pay the deductible before receiveing the benefit, and your co-payment is usually less.. With PPO, you do not have to choose a primary care physician, and you can go to the speicialist by yourself.You do not necessarily have to limit yourself to the PPO network, but then the cost is little more, like if you go to doctor within PPO they cover 90% of the cost, and if you go outside their network, it only covers 70% of the cost. aslo with PPO, you have to meet your deductible ,for hospitalization, before your benefit begins, and usually they have a higher co-pay .