Some colleges offering self-financed tertiary programmes are in dire straits in the face of intense competition, with student intakes as low as zero.
Educators say the market has become crowded as a growing number of institutes seek to offer courses to students who have failed to get into a government-subsidised university.
About a fifth of the 30 non-subsidised tertiary institutes have filled less than half of their programmes' places for the current academic year, according to figures released by the Education Bureau.
Hong Kong Adventist College in Sai Kung had no takers for any of the 40 places in its sub-degree programmes. Pui Ching Academy in Yau Ma Tei, which offered 150 sub-degree places this year, got only three students, while Yew Chung Community College in Sham Shui Po has 44 students in its sub-degree programmes, leaving 376 empty places.
Hong Kong Buddhist College in Lai Chi Kok has 19 people enrolled in its sub-degree programmes, which offer 300 places.
Professional Teachers' Union president Fung Wai-wah said many education groups wanted a share of the tertiary market.
"But they failed to realise that the competition is intense and the cake is small," he said.
Fung said most secondary-school graduates aimed for undergraduate spots in the eight subsidised institutions and if they failed, they would choose self-financed undergraduate or sub-degree programmes in institutes with a relatively long history and good reputation.