PayPal is teaming up with Parkmobile to make paying for parking even easier.

In a blog post today, PayPal announced that Parkmobile users can access the payment service to pay for parking in 20 cities across the United States. Once you’re set up with Paypal, it only takes one click to purchase time in a space.

Thankfully, I don’t have to pay for parking where I live, but the app seems to work pretty easily.

Drivers need to look for a green Parkmobile sign on designated spaces to use the service. Once parked, users need to open the app to activate the session and key in a parking zone number. After that, drivers can now feed the meter directly with their PayPal account.

The app also sends alerts and reminders 15 minutes before a parking session is about to expire. Users then have the option of paying for more time on the meter. Other features include the ability to save frequently parked zones and use GPS to find a vehicle.

Parkmobile can also save receipts for easy expense reporting.

More than 4 million drivers in more than 350 cities are already using the service. And the PayPal integration should help that number continue to rise.

Parkmobile, designed for the iPhone/iPod and compatible with the iPad, can be downloaded now in the App Store for free.