Asia is undergoing tremendous economic development and increased demand for energy, particularly from coal burning. As a result, acidic precursors move to neighbouring countries with the potential to cause serious environmental damage. Such transboundary pollution originating from countries in the Asian region such as India, China and Thailand contribute to acidic depositions in Sri Lanka. India in particular, because of its geographical proximity contributes significantly to sulphur depositions in Sri Lanka. The RAINS-ASIA model was used to calculate future acidic depositions in four major cities of Sri Lanka for the period 1990 -2030 using baseline data from 1990. The total acid depositions due to Sri Lanka taken as a whole can be compared to those arising from transboundary pollution. It was found that the acidic depositions in all four cities will increase by 400 -600 % during this period, with Kandy recording the highest increase at 600 %. It was also found that the share from transboundary pollution to acid depositions in Jaffna located close to the Indian peninsula is ~80 % of the total. On the other hand, the transboundary contributions in Colombo is predicted to decrease from 58.5 % in 1990 to 33 % in 2030. This can be attributed to increased local air pollution, resulting from the burning of fossil fuel such as coal and diesel in local power stations and also increased vehicular traffic. Ship movements around Sri Lanka significantly contribute to acid depositions and depending on the city it can vary from 10 -15 %.