Can leaving up old web pages no longer accessible through my site navigation hurt my rankings?

[matt-14567]

My firm recently overhauled a client's website. As part of the project, we gave the content a new structure, eliminating certain pages and creating several new ones.

However, I just found out that some of the "old" pages (the ones we supposedly eliminated) still appear in the Google SERPs. Somehow, the client - who handled the coding - let these pages remain live even though they can no longer be accessed through the site navigation.

This seems like something that could hurt the client's SEO rankings, but I want to make sure before contacting the client and suggesting they take down the old pages.

Can anyone confirm my suspicion?

[DanSpeicher]

301 redirect the pages to new and relevant content if the pages are receiving traffic.

If they aren't receiving traffic, I'd take them down.

[matt-14567]

Thanks for the quick response.

Would the client risk being penalized by Google by leaving the old pages up?