Plaintiff failed to serve Dr. Naseh within the required 120-day period after filing (CPLR 306-b), and did not move for an extension of time to serve until faced with a motion to dismiss, approximately seven months after the 120-day period had expired, and more than three years after the cause of action had accrued. Moreover, plaintiff failed to demonstrate that her action had merit. In view of such lack of diligence and the long delay in notifying Naseh of this action, which caused him substantial prejudice, an extension of time to serve was unwarranted, and dismissal was appropriate ( Slate v Schiavone Constr. Co., 4 NY3d 816; Ekbatani v Rockefeller Ctr. Props., 30 AD3d 347).