NEW YORK —Those smiley door greeters are back at Wal-Mart.

Four years ago, the discounter decided to remove the greeters at the front of the store and relocate them to other areas. But the nation’s largest retailer said in a blog post this week that it’s bringing back the greeters to a majority of its 5,000 stores by midsummer to improve customer service. Greeters were a tradition started by the company’s late founder, Sam Walton.

At stores that have been selected as higher risks for thefts, Wal-Mart will position a “customer host” who not only will greet customers, but also will check receipts to prevent theft. That was flagged as a growing problem last year. Those workers will be trained to help deter potential shoplifters.

The return of greeters comes as the retailer based in Bentonville, Arkansas is working to improve sales and service amid fierce competition from outlets ranging from dollar stores to online leader Amazon.com. The company has seen gains in a key revenue measure for six straight quarters at its Wal-Mart U.S. division, but the increases have been mostly small.

“Providing customers with an excellent first impression is part of Wal-Mart’s broader strategy to ensure simpler, more convenient shopping,” Mark Ibbotson, executive vice president of central operations for Wal-Mart’s U.S. division, wrote on the blog. “Focusing more on our greeters is one of a whole host of details we’re looking at – it just happens to be a very visible one.”

Wal-Mart is aiming to boost sales by improving the experience in the store through other ways as well. It has increased wages for its hourly workers, made the stores cleaner and has opened up more cash registers during busy times.