The UGA sites says:
http://www.uga.edu/nchfp/how/freeze/cherry_sweet.html
Freezing Cherries – Sweet

Preparation – Select bright, fully ripened cherries of dark colored
varieties. Wash, stem and pit.

Syrup Pack – Use cold, 40 percent syrup. For a better quality product add
1/2 teaspoon (1500 mg) ascorbic acid to each quart syrup. Pack fruit and
cover with syrup, leaving headspace. Seal and freeze.

And
http://www.uga.edu/nchfp/how/freeze/cherry_sour.html
Freezing Cherries – Sour

Preparation – Select bright red, tree ripened cherries. Wash, stem and pit.

Syrup Pack – Pack cherries into containers and cover with cold 50 per cent
syrup. Leave headspace. Seal and freeze.

Sugar Pack – To 1 quart (l1/3 pounds) cherries add 3/4 cup sugar. Mix until
sugar is dissolved. Pack into containers, leaving headspace. Seal and freeze


I was looking through a list of sites and another site said: "Although it
is safe to freeze cherries with pits left in them, it is not very efficient.
Since you would never serve cherries in any recipe with the pits." This was
not on the UGA or another educational site but it made sense to me so I
wanted to share it with you.

http://web1.msue.msu.edu/imp/mod01/01600378.html
The Michigan State University Extension says:
Preserving Food Safely - 01600378
08/03/99
FREEZING CHERRIES
Cherries, sour
Whole
Syrup pack is best for cherries to be served uncooked.
Sugar pack is preferable for cherries to be used for pies
Or other cooked products.

Select bright-red, tree-ripened cherries. Stem, sort and
Wash thoroughly. Drain and pit.

Use one of the following methods.
Syrup pack
Pack cherries into containers and cover with cold 50-
Percent syrup, (1 cup water to 1 cup sugar) depending
On tartness of the cherries. Seal, label and freeze.

Sugar pack
To 1 quart (1 1/3 pounds) cherries add 3/4 cup sugar.
Mix until sugar is dissolved. Pack into containers.
Seal, label and freeze.

Crushed
Prepare for packing as freezing whole. Remove pits and
Crush cherries coarsely.
To each quart (2 pounds) of crushed fruit add 1 1/2 cups
Sugar and 1/4 teaspoon ascorbic acid. Mix well. Pack into
Containers. Seal, label and freeze.