While Cuba was still firmly in the communist camp and ostracized by the West, there was little chance of her recovering her lost property, or even tracking down what had become of it. But now Cuba is coming in from the cold, opening up parts of its economy and, most important, mending fences with the United States. And at last, Spaniards like Ms. Álvarez-Varcácel see a chance to press their claims in Havana and eventually get compensation, if not restitution.

Some diplomatic obstacles have been falling away, now that President Obama has decided to improve relations with Cuba. On May 29, Washington removed Cuba from its list of state sponsors of terrorism, and the two countries agreed this month to reopen embassies in each other’s capitals.

But a major hurdle remains: Spain and Cuba signed an agreement in 1986 in which Cuba agreed to pay about $40 million in compensation for seized assets over a 15-year period, partly in cash and partly in goods like tobacco.

Whether that agreement was the final settlement of all Spanish claims is unclear.

The claimants hope not. They see the détente between Washington and Havana as “very good news, because it shows change is underway in Cuba,” said Jordi Cabarrocas, the director of the 1898 Company, an investment fund that represents some Spaniards whose property was seized. “There will be more twists and turns, but what’s important is that Spaniards don’t miss out on the changes in Cuba.”

Still, the Cuban government has lately shown no inclination to discuss expropriation claims. The Cuban Embassy in Madrid said it had no comment on the issue.