PPO plans and HMO plans have the following similarities:

• They’re both offered through private Medicare-approved insurance companies 
• 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
• Both require you to have Original Medicare and to live within the plan’s service area, like any Medicare Advantage plan

But there are key differences between these plans:

• PPOs allow you to see doctors outside of your plan network, although you typically have to pay higher copayments or coinsurance to see these providers
• HMO plans require you to choose a primary care doctor, but PPO plans do not (offering you more flexibility) 
• HMO plans usually require you to get a referral to see a specialist, while PPO plans do not

In general, PPO plans are less reliant on a network of providers than HMO plans. They offer you more flexibility and freedom with access to more health care providers in more locations, but they usually cost more than HMO plans.