The city Health Department says its year-old ban on smoking at parks and beaches is showing results.

The department conducted a survey of 13 parks in Manhattan and Brooklyn in the fall of 2011 and found that smoking had declined by two-thirds compared to a year earlier.

The rule against smoking in parks and on city beaches took effect in May of last year.

The Health Department also found that tobacco litter on beaches declined by about two-thirds between the summers of 2010 and 2011.

Health Commissioner Dr. Thomas Farley said yesterday that the ban has made parks and beaches cleaner and safer for everyone.