HMO plans and PPO plans have the following similarities:

• They both cover full Original Medicare benefits
• They both typically include Medicare Part D (prescription drug coverage) and may have preferred pharmacy networks
• They both use provider networks
• They’re both offered through private Medicare-approved insurance companies 
• Both require you to have Original Medicare and to live within the plan’s service area, like any Medicare Advantage plan

But there are important differences between these plans:

• HMOs are more strict with their provider networks, while PPOs allow you to see doctors outside of your plan network
• HMO plans require you to choose a primary care doctor, but PPO plans do not 
• HMO plans usually require you to get a referral to see a specialist, while PPO plans do not 

HMO plans are the most reliant on a network of providers. You get less flexibility and freedom, but access care at a lower cost than a PPO plan.