Polls predicted a victory for parties campaigning for the rich north-eastern region to become "Europe's next state".
However, such a vote would put Catalonia on a collision course with the conservative government of Mariano Rajoy, which has vowed to try to block any home rule referendum as unconstitutional.
Catalans went to the polls yesterday amid a sea of pro-independence flags. The estelada – a version of the Catalan flag inspired by the banner of Cubans fighting Spanish rule more than a century ago – was hung from balconies throughout Barcelona.
Catalan President Artur Mas has used increasingly pro-independence rhetoric in the run-up to the election, which he called after he tried and failed to argue for fiscal autonomy.
Many Catalans believe they are taxed unfairly, losing some 8% of their GDP to the rest of Spain.
Rosabel Casajoana, 64, a teacher, said: "The economic crisis has made the difference."
Overall support for Catalonia to declare independence – an idea that experts stress has still to be strictly defined – has leapt from about one-quarter of Catalans just two years ago to around half today.
The rise has coincided with threats from Madrid that included calls for the Catalan education system to be "hispanicised".
Mr Mas has called on voters to give him the kind of support the SNP's Alex Salmond received in his landslide win last year to help him push through an independence referendum. His centre-right coalition of moderate nationalists, Convergencia i Unio (CiU), is forecast to win, but not with the kind of landslide Mr Salmond secured at Holyrood.
Instead, pollsters suggest, the alliance will attract enough votes to form a minority administration, such as that of sovereigntists in Quebec earlier this year.
"Will it be a majority like the one in Scotland, where they could have a referendum, or like the one in Quebec, where they could not?" Mr Mas asked voters last week. "That will depend on you."
Professor Michael Keating, of Aberdeen University, reckons there is still a lot more to Catalan politics than independence.
He said: "There will be an independence majority because the left-wing nationalist party Esquerra Republicana will do well.
"So Mr Mas could get a majority for some kind of sovereignty in the parliament but not for the CiU. But if he does a deal with the Esquerra that will cause problems for his own coalition.
"CiU are two parties and the Unio doesn't want to get in to bed with the Esquerra. And Mr Mas has got to find a coalition not just to hold a referendum but govern."