A method is provided for operating a diesel engine exhaust aftertreatment system including a DPF and a LNT. The LNT is regenerated as soot is combusting in the DPF. To accomplish this, reductant is injected between the DPF and the LNT during soot combustion, whereby the LNT experiences rich conditions as the DPF experiences lean conditions. Preferably, the DPF is of small size whereby the DPF is heated easily and needs to be regenerated almost as often as the LNT needs to be denitrated. In an exemplary process, DPF regeneration begins in response to a control signal to denitrate the LNT. Preferably, the reductant is diesel fuel and there is a fuel reformer between the DPF and the LNT. Oxygen consumed by soot combustion reduces the fuel penalty for regenerating the LNT and promotes stable reformer operation. Heat generated in the DPF helps warm the fuel reformer.