All eyes were on Slovakia as ECB chief Mario Draghi finally did what was long expected and cut interest rates by 0.25pc. The decision to bring the benchmark rate to a record low 0.5pc spurred some markets, but didn't quite result in a big kicker for stocks.
Better-than-expected results from firms including BMW and Shell also buoyed markets, while the US Federal Reserve also said that it would continue to buy $85bn (€65bn) worth of bonds every month and would raise or lower that amount depending on economic circumstances.
"Our monetary policy stance will remain accommodative for as long as needed," Mr Draghi said. "We are closely monitoring money market conditions and their potential impact on our monetary policy stance and its transmission to the economy."
"The fashion right now for all central banks is to help the economy with a lot of money, and this will go on, and this will lead equity markets higher," said Herbert Perus, who helps oversee $36bn as head of equities at Raiffeisen Capital Management in Vienna.
In Ireland, the ISEQ Overall Index edged just 0.63pc, or 24.52 points, higher to end the session at 3,890.26.
Main gainers included Grafton Group, which advanced 1.5pc, or almost 8c to €5.33. It rose after UK firm Howden Joinery said it had a good start to the year with organic revenue growth of 4.1pc.
Shares in Ryanair rose nearly 2.1pc, or 12c, to €6.09. It climbed after it said the number of passengers it carried in April was 2pc higher year-on-year at 7.4m.
Elan was virtually unchanged in Dublin at €8.74 after US firm Royalty Pharma confirmed its $11.25 per share offer for the Irish company.
National benchmark indices declined in nine of the 18 Western-European markets. Germany's rose 0.6pc, while the UK's FTSE 100 added 0.2pc and France's CAC 40 increased 0.1pc.
Shell rose 1.4pc to €26.20 in Amsterdam. Europe's largest oil company said first-quarter profit, excluding one-off items and inventory changes, rose 3pc to $7.5bn from a year earlier. That beat the $6.4bn anticipated by analysts.
BMW advanced 1pc to €70.74. The world's biggest luxury-car maker said first-quarter earnings before interest and taxes declined to €2.04bn, a smaller drop than analysts had predicted.
Beiersdorf climbed 4.2pc to €71.64 after the maker of Nivea skin cream reported first-quarter Ebit that exceeded estimates. Emerging-market sales, which contribute almost half of total revenue, jumped.
Danske Bank slipped 5.4pc to 103.10 kroner. Denmark's biggest lender also reported net income of 1.47bn kroner (€197m) in the first quarter.
Analysts had predicted 1.57bn kroner of profit for the period. In Ireland, Danske said it would incur further impairments totalling €335m between this year and next.