As part of the study researchers surveyed around 3,700 children in four parts of Kenya.
The study noted that in 2004 almost all ITNs available in Kenya were sold commercially and only 7 percent of children slept under nets. Also, in the poorest families, who are most at risk of malaria, only 3 percent slept under nets.
During 2005 ITNs became increasingly available, heavily subsidised in clinics, and an increase in the overall level of use to 24 percent.
Free mass distribution began in 2006 and by the end of that year two-thirds of children were sleeping under nets.
The study has found that a free mass distribution programme has raised the rate of ITN use to an impressive 66 percent.
The researchers suggested that ITNs must be available free if high levels of use are to be achieved. This will cost money but will save many lives.
The findings of the study were published in PLoS Medicine.