“This is great news for seniors on Medicare,” Paul Nathanson, executive director of the National Senior Citizens Law Center, a nonprofit advocacy group, said in a conference call on Thursday after the Supreme Court issued its ruling upholding the Affordable Care Act.

Because several key provisions involving Medicare kicked in soon after Congress passed the bill in 2010, many beneficiaries won’t see big changes in their coverage now. But those improvements could have evaporated had the law been overturned, so the ruling generated sighs of relief among advocacy organizations for older adults.

This means the annual free wellness exam will continue (about 2.2 million people took advantage of it last year, according to AARP), along with the first “Welcome to Medicare” visit, which will remain free, with no out-of-pocket costs.

A number of preventive services, including mammograms, bone scans and depression and diabetes screenings, used to involve deductibles and co-pays; under the Affordable Care Act, they no longer do.

And the gradual closing of the dread “doughnut hole” gap in Part D drug coverage by 2020 will proceed, bolstered by discounts that have already lowered drug costs. “The average Medicare beneficiary will continue to save an average $650 a year,” Max Richtman, who leads the National Committee to Preserve Social Security and Medicare, said in Thursday’s teleconference. “That’s real money, especially for seniors.”

On the long-term care front, the court’s action preserves several initiatives advancing efforts to support elderly and disabled people in their homes, rather than in nursing homes.

Several are already under way, including the Community First Choice Option, which assists states with the costs of in-home programs for people who would otherwise be institutionalized, and the Balancing Incentive Program, which increases federal matching Medicaid funds in states with less coverage for home and community services.

And starting in 2014, the Affordable Care Act will help husbands and wives hold onto more of their assets if a spouse must spend down to qualify for Medicaid.

Provisions that strengthen efforts to cut Medicare abuse and fraud will survive as well. And if the economics work as the Obama administration planned — a fairly big if — Medicare as a whole stays solvent longer.

One murky question concerns Medicaid, and the court’s ruling that states that don’t agree to expand their coverage can’t be penalized by losing their current financing. This could affect millions of people, but “we’re not exactly sure of all the ramifications,” Mr. Nathanson acknowledged.

Many states might agree to the expansion anyway, said Kevin Prindiville, deputy director of the National Senior Citizens Law Center. “The states get a great deal,” he said. “The feds pick up most of the costs.”

Amid the general applause from advocates for the elderly, several leaders said they foresaw ongoing Medicaid tussles with Congress and state governments. But for now, they were all smiles.

“A great win,” Mr. Prindiville said. “The act is going to improve health for seniors in a variety of ways.”