The Scottish Qualifications Authority has apologised to students who were due to receive exam results online but received blank emails instead.
The SQA said it acted urgently and found a technical issue which it has now resolved.
Only candidates who signed up to receive results by email were affected, the SQA said.
Around 145,000 pupils in Scotland received exam results on Tuesday for a range of qualifications including National 5, Highers, Advanced Highers and SQA Awards.
In England, A-Level results are published on Thursday August 15, and GCSE results on Thursday August 22.
A spokeswoman for the SQA said: “We have resolved a technical issue that impacted candidates who signed up to receive their results by email only using the MySQA service.
"Texts were not impacted and the vast majority of learners who signed up to MySQA received their results as expected.
"We apologise for any concern caused to learners who experienced a delay before receiving their MySQA email with their results attached."
Sue Webber MSP, convener of Holyrood's education, children and young people committee, said: "I am upset for pupils, and their teachers, that emails without results on them were issued.
"While we understand the issue has now been resolved, our committee, like the thousands of pupils affected, will be keen to know what happened and ensure that it is not repeated."
This year's results in Scotland showed that 77.2 per cent of those sitting National 5 exams passed with grades A to C - down from 78.8 per cent in 2023.
For Highers, 74.9 per cent of students passed with the top bands, down from 77.1 per cent last year, and for Advanced Highers 75.3 per cent of students achieved A to C grades, falling from 79.8 per cent in 2023.
The SQA stressed "significant caution" should be exercised when comparing results, as changes during and after the pandemic have meant that different approaches have been used in awarding examsevery year since 2019.
Education Secretary Jenny Gilruth said Scotland's education system is "still in recovery from the pandemic".
She added: "Undoubtedly, that has contributed to some of the variability we have seen in results this year, particularly with the full return to qualifications requirements for the first time since the pandemic.
"I am determined to work with our teachers, school staff and local authorities to drive further improvements in our schools.
"The curriculum improvement cycle is already under way, with mathematics and numeracy being prioritised first, which is being led by the recently appointed new national specialist in mathematics.
"In the coming weeks, I will publish the Behaviour Action Plan, set out new action to improve attendance and confirm the Scottish government's next steps on qualifications reform early in the new parliamentary term."
Ms Gilruth said she was also conscious there is a "wide degree of variation in results" between Scotland's 32 local authorities.
A special results helpline has been set up on 0808 100 8000.
