In the past, concentrated efforts were directed at developing a cost effective and reliable particulate trap, assisted by mechanical (burners) or electrical (heating elements) regeneration means. Although ceramic monolith filter developments have been straightforward, regeneration systems have proven to be problematic and costly. Therefore, these development efforts led to disappointing results.Using catalytic fuel additives to promote regeneration in a trap through lowering the incineration temperature of collected soot is an attractive alternative. This passive form of regeneration could be technically and economically advantageous for diesel applications by eliminating complex sensors and controllers required for regeneration systems in new installations as well as retrofitting older vehicles.A cerium based fuel additive was used to assist in regenerating particulate traps in diesel exhaust aftertreatment. Although positive results were obtained in applications where this additive was utilized, some potential users as well as environmentalists suspect that it may cause deterioration in gaseous emissions characteristics.This paper is written in anticipation of questions regarding potential emissions of harmful compounds which could be related to cerium fuel additive. It describes the effect of this additive on the regulated and some unregulated emissions in a North-American heavy-duty diesel engine.