Cynthia Greenwood's three girls always get new sleepwear at Christmas, the only gift they are allowed to open on Christmas Eve. The sisters waste no time getting comfy before the family sits down to a holiday dinner and relaxes by the fire.

“They come right in from church, they look under the tree and there's the box of PJs, and they run back to their room and put them on and we start the festivities,” said Greenwood, of Arlington Heights, Ill. “It's just a really nice night. It's special.”

The tradition has been going strong for about two and a half decades in the Greenwood home: The sisters, now 31, 28 and 23, have seen their gifts evolve from one-piece footed numbers to matching ruffled nightgowns to two-piece pajama sets.

New pajamas are a holiday custom in many families and a perennially popular gift, whether it's Mom and Dad outfitting the kids in coordinating PJs for keepsake photos, a husband or wife tired of seeing their spouse in the same old ratty nightwear, or a treat for a special friend.

“Getting sleepwear is very nostalgic,” said Jennifer Wilson, associate corporate merchant for L.L. Bean. “You're giving the gift of warmth and comfort. It's cozy but it's practical at the same time.”

People spend a lot of time in their PJs, often changing into them right after work, snuggling up on the couch to watch a football game or even wearing them out of the house, noted Stacey Buonanno, director of product development for online retailer PajamaGram.

“People are trying really hard to carve out family time together and relaxation time, whether it's playing a game together or watching a movie. A lot of that time happens in your PJs or sweats,” said Buonanno.

Pajamas also make a great gift because many people neglect to buy them for themselves, she added.

And sleepwear is easier to buy for someone else than a sweater or pair of jeans because you don't need to worry about the perfect fit. “With PJs, just go up a size if you're not sure and say you wanted them to be comfortable,” Buonanno said.

There are a lot of choices when shopping for jammies. Does your guy like a classic button-front or pullover style? Do the kids need fleece or cotton? Does the lady in your life prefer a gown (short or long? sexy or demure?) or a two-piece set? Will your recipients appreciate the whimsy of a reindeer eating a candy cane or do they expect a traditional tartan?

A look at some options:

Kids

For parents, there may be nothing cuter (or more relief-inducing) after a long day of holiday celebrations than seeing the kids all washed up for bed and in new PJs.

Matching family set — the same print for men, women, children and pets — are a hit at PajamaGram, with orders quadrupling over the last few years, Buonanno said. The company's most popular family looks are a red Stewart plaid and the holiday stripe: red, green and white striped pants with coordinating red and green tops.

If matchy-matchy isn't your thing, there are countless choices for kids to show off their individuality. At Kohl's, look for sleepwear featuring a favorite team, a beloved cartoon character or a cool design, like camouflage. Old Navy offers a festive Santa suit PJ set for babies and toddlers, superhero PJs for boys and Hello Kitty sets for girls.

Women

PJs are more popular than nightgowns, retailers say, but there are many holiday options in both styles.

At L.L. Bean, the ankle-length tartan flannel nightgown and pajama come in a traditional red royal Stewart and in colors new this year: a light blue and a blackwatch plaid that includes a shot of bright pink.

“The gowns would be great for your grandmother and the flannel PJs might be perfect for your sister,” Wilson said.

For a less “high holiday” look, or if you are not sure what a woman likes, Wilson suggests Bean's pima cotton flannel PJs in a cornflower blue with white dots. “It's got a pretty universal appeal,” she said.

PajamaGram offers everything from button-up PJs to satin ones to pretty gowns, but a best-seller is the Hoodie-Footie, a grown-up version of the infant sleeper. The one-piece fleece has a hood, zip-off feet and pockets.

“Men love to buy them for their wives and girlfriends,” Buonanno said. “It keeps her warm from head to toe, plus she looks really cute in it.”

Men

The classic button-front and the pullover style are equally popular at PajamaGram. At L.L. Bean, Wilson likes the fleece sleep bottoms, the monochromatic waffle-knit PJs and the scotch plaid flannel PJs, which come in several color combinations.

Look for one-piece footed PJs from online retailer Jumpin Jammerz, which offers prints showing “Star Wars,” Kiss and the Hulk.

While winter-themed and red and green sleepwear is never in short supply, nightwear celebrating Hanukkah and Kwanzaa for adults can be found online at CafePress, and PajamaGram has a Hanukkah design as well.