In the new Google+ pages,
You can go back and see posts and comments you've +1ed by checking your Activity Log. You can also remove your +1 using the Activity Log.
To do that, go to Settings and click on the Activity Log link.
From there, you can see all your +1.
If you want to see posts you’ve +1’d on Google+, check out your Activity log. If you want to see the things you’ve +1’d outside of Google+, you can visit the +1s tab on your Google+ profile.
- Open Google+.
- Near the top left corner, click the drop-down arrow > Profile.
- Under your cover photo, click the +1’s tab.
Android app / Mobile browser / iPhone/iPad app
You can’t see your +1s on a mobile device just yet. Please check out the +1s tab from a computer.
You'll find your full list of +1's in a special tab on your public Google profile.
So basically, go to your Google+ profile and click on +1's