Two men entered the Polish Town Deli on Pulaski Street in Riverhead Sunday night, one flashed a knife, and they demanded money from the clerk, Riverhead Town police said.
They got only cigarettes, police said, and ran off.
Police said they found and arrested one of the men a short time later on Peconic Avenue. They are still searching for the other man, they said.
Jed P. Stout, 19, of Muellers Lane, Yaphank, was charged with first-degree robbery, police said. Arraignment information was not immediately available.
The incident took place at 10:27 p.m. No one was injured.