New figures show there were 2407 such students in the further education sector in 2012 compared to more than 2700 the previous year.
The fall has been blamed on a Scottish Government decision to concentrate provision on full-time courses that lead to recognised qualifications.
Peter Scott, chief executive of charity Enable Scotland, said the figures highlighted "diminishing opportunities" in colleges for people with a learning disability.
"Like anyone else these students want to learn, work, earn a living and fully participate in society," he said.
"These courses are crucial in terms of gaining employment and help people become more confident through learning new skills."
Penny Gower, president of the EIS-FELA union, said students with disabilities were being hit hard. "This is because the climate is one of major cuts which have bitten deep, alongside wholesale reorganisation through merger," she said.
"Added to this, the government's programme is to narrow the scope of the service to a particular age group towards courses which gain nationally recognised qualifications and towards employability."
A spokesman said the Scottish Government was committed to "ensuring students with a learning disability receive an improved educational experience, which is tailored to their needs and ambitions".
"We have funded the employment of dedicated support officers and development of a new good practice guide using an additional £250,000, which will assist 200 students to progress from learning to employment over the next 12 months," he added.