A Sydney restaurant has been questioned by NSW Police over its "unsavoury" and "antisocial" wine list.

The restaurant, 10 William Street in Paddington, was advertising "wine by the glass" on its blackboard when NSW Police entered the small Italian-style bar on Saturday night.

Police told the venue's manager that they were concerned the blackboard was too close to the front of the terrace-turned-candlelit bar and could encourage heavy drinking.

Police also raised concerns about a sign on the front of the restaurant advertising wine without additives as "free wine" said the restaurant's owner, Giovanni Paradiso.