The 25-year-old actress was seen getting cosy with Ronson, who she dated for two years from 2007 to 2009, at New York nightclub Le Baron last week, reports femalefirst.co.uk.
"Lindsay and Sam were whispering and laughing and they left the club holding hands. They didn't care who saw them and they definitely seem to be back on. It was just like the old days, they couldn't get enough of each other!" a source told X17 Online.