Without the line-of-sight limitation, plasma immersion ion implantation (PILI) emulates conventional beam-line ion implantation in inner surface modification of industrial components. However, dose uniformity on the inner surface is critical. Inner surface PIII of a cylindrical bore is modeled using a two-dimensional fluid model. It is found that the retained dose is not uniformly distributed on the inner surface and the maximum dose is observed away from the edge. The exact location of the maximum dose, which varies with the implant pulse duration, is closer to the center when the pulse width is longer. The maximum relative difference of the retained dose along the interior also depends on the implant pulse duration. It is smaller for a longer pulse duration after a threshold value has been exceeded.