Better communication is needed with the organisers of Tartan Week events, a report has found.
Tartan Week traditionally involves a parade in New York
The Scottish Executive commissioned the evaluation of the annual celebration of Scots history and culture, which takes place in the US in April.
The executive funded 15 events in New York, Boston and Washington during the nine-day event this year.
But the study said event organisers only found out how much cash they would be receiving in January.
The executive spent £558,000 on enabling Scottish organisations to stage Tartan Week events, with a further £100,000 going on marketing.
The report said this had been a "successful" investment, gaining more media coverage in the US and in Scotland than the previous year.
However, it said there should be better communication and highlighted that many of the negotiations with individual organisations were not in written form.
"This led to miscommunication, particularly surrounding availability of funding," said the report.
"Letters confirming level of funding were not distributed to event organisers until January 2006, giving little time for event organisers to plan their event and secure appropriate venues and speakers."
The report also said it would be beneficial to have one individual who was recognised as being in overall charge of Tartan Week.
An executive spokesman said: "The whole reason we carried out this evaluation was so we could improve the way we deliver Tartan Week.
"The people involved in Tartan Week 2007 have had earlier notification of their funding, and they have certainly been far more positive about the process this time round."
Tartan Day was first formalised by the US Senate in 1998 to mark the Declaration of Arbroath on 6 April 1320, when a group of Scottish nobles swore independence from England.
It has since been extended to cover a whole week of events.