Marketers know that smart phones and tablets are increasingly part of the “path to purchase” for many consumers, but how big a role did they play in purchasing decisions this past holiday season?

According to Google, a big one.

For smart phones, Google says that 46% of device owners researched a product or service on the device and went on to make a purchase offline and that 37% did smart phone-based research followed by a desktop computer purchase. Interestingly, 41% of smart phone owners performed their research and completed a purchase on the device.

What role did smart phones and tablets have in the purchasing process? Both smart phones and tablets were both popular tools for reading product reviews and comparing prices. Smart phones were particularly popular when it came to searching for a store’s inventory and contacting a retailer, but somewhat surprisingly, consumers still far preferred using the desktop to search for discounts and coupons.

According to Google, “The first key mobile insight every advertiser should know is that consumers use their smartphones at many different points during the purchase path.” This means that marketers will need to be careful not to look exclusively at the ‘last click’ if they want to understand how mobile devices are driving sales. Case in point: some 19% of smart phone owners researched a product on their phone, visited a store to look at the product, and then went home to purchase the product using a desktop computer or laptop.

Of course, for many companies, tracking consumers as they move to and from mobile, web and physical presences is not the top priority. As Google notes, having a mobile-optimized site and providing a “seamless experience between online and offline in-store”, something many businesses haven’t yet established, is the first step for success in 2012.