When Google first made the switch from the AdWords “legacy” platform to the now not so new “enhanced” platform I wrote in a blog that at that point in time whether or not your website was responsive or mobile friendly was not an issue but that down the road it almost certainly would become a factor.

It becomes a factor April 21st 2015.

The below comes direct from Google:

“When it comes to search on mobile devices, users should get the most relevant and timely results, no matter if the information lives on mobile-friendly web pages or apps. As more people use mobile devices to access the internet, our algorithms have to adapt to these usage patterns. In the past, we’ve made updates to ensure a site is configured properly and viewable on modern devices. We’ve made it easier for users to find mobile-friendly web pages and we’ve introduced App Indexing to surface useful content from apps. Today, we’re announcing two important changes to help users discover more mobile-friendly content:

1. Starting April 21, we will be expanding our use of mobile-friendliness as a ranking signal. This change will affect mobile searches in all languages worldwide and will have a significant impact in our search results. Consequently, users will find it easier to get relevant, high quality search results that are optimized for their devices.

In other words – if someone is searching for a product or service you offer on a mobile device and your website is not mobile friendly while your competitor’s website is mobile friendly – your competitor’s ad will show and most likely – your’s will not!

2. Starting today, we will begin to use information from indexed apps as a factor in ranking for signed-in users who have the app installed. As a result, we may now surface content from indexed apps more prominently in search. To find out how to implement App Indexing, which allows us to surface this information in search results, have a look at our step-by-step guide on the developer site.”

What this means is that if you offer an app and someone uses that app, that is factored into their search results.

To see how your website fares regardless mobile-friendliness you can use this tool: https://www.google.com/webmasters/tools/mobile-friendly/