Female directors of UK firms work longer than their male counterparts but earn on average 19% - or £14,028 - a year less, a study suggests.
The basic average salary of a male UK business director is £74,028
And the gender pay gap in the voluntary sector is about 25%, the Institute of Directors (IOD) report said.
Most directors, whether male or female, had only "moderate" pay rises last year and fewer than 50% of managing directors got company cars, it added.
The 'fat cat' image of Britain's bosses was misleading, the report claimed.
It found that the average female director earned £60,000 and worked 51.25 hours a week in a small-to-medium company and 57 hours in a larger firm.
Their male counterparts had an average basic pay of £74,028 and spent on average 50 hours at work or 55 hours at a larger firm - described as one which turned over between £50m and £500m a year.
"Although there has been a decrease from a 24% gap to 19% this is hardly grounds for celebration", said IoD general director Miles Templeman.
"Even those who break through the glass ceiling and reach board level will find there's another roof over their heads."
The average director had a 3.2% pay rise last year, the IoD said, with "significant " numbers not taking all of their holiday entitlement.
The IoD study, with pay consultancy group Croner Reward, looked at 3,815 director jobs at about 1,000 organisations.
It found considerable regional disparities with London-based directors earning more than 30% more than directors in Northern Ireland.
In the East Midlands, the average director earned 3.2% above the average national rate, while those in Scotland and North West England were paid 11% to 21% below that level.
"It's right that directors' pay is coming under ever increasing scrutiny but we need to highlight the clear distinction between the FTSE 100 and the vast majority of businesses which make up UK plc," Mr Templeman said.
A separate study by the Chartered Management Institute (CMI) found that women managers were still being paid on average £5,147 a year, or 12%, less then men.
This was despite the female bosses having gained bigger pay rises than their male counterparts for the 10th year in a row.
Its survey found that the average salary, including bonuses, for female managers rose in 2005 to £43,521, while men earned £48,668.