Due to their light weight, excellent high-temperature mechanical properties, chemical inertness and selflubricating capability, carbon/carbon (C/C) composites have been used as aircraft brake material for decades. The C/C composites, most often used as aircraft brake disks, are comprised of either polyacrylonitrile (PAN)-based carbon fiber (fabric laminates)-reinforced chemical vapor infiltrated (CVI) matrix or mesophase pitch-based carbon fiber (chopped yarns)-reinforced phenolic resin char-CVI hybrid matrix composites [1]. Much research has been devoted to investigation of the relationship between tribological behavior and testing parameters, such as sliding speed, break-in speed, humidity, load, surface condition and additives, of a series of two-dimensional (2D) C/C composites [2–9]. The effect of a post-treatment comprising reimpregnation of a carbonaceous additive-doped liquid precursor on tribological performance of a fastcarbonized PAN/phenolic-based C/C composite has been discussed in a previous study [10]. According to the study, after the post-treatment, all samples demonstrate decreases in both COF (coefficient of friction) and weight loss. The results indicated that an appropriate post-treatment may dramatically improve the tribological performance of the PAN/phenolic-based C/C composite. The purpose of the present study is to verify whether this simple treatment is also capable of improving the tribological performance, especially reducing wear rate of two other 2D C/C formulae (PAN/CVI and pitch/phenolic/CVI), which are among the most popularly used C/C composites for aircraft brake disk today. Preparation methods and properties of the pitch/phenolic/CVI (designated “A”) and PAN/CVI (designated “B”) composites have been described in an early study [11]. The post-treatment was conducted by first impregnating the composites with a carbonaceous additive (1 wt%)-doped liquid precursor in vacuum. Based on the earlier results [10], the two most-promising liquid/additive combinations—furan resin/carbon black (designated “FB”) and coal tar pitch/mesophase pitch powder (designated “PM”) were selected for the study. The impregnation of the carbon black-doped thermosetting furan resin with a relatively low viscosity was carried out at room temperature. The impregnation of mesophase pitch powder-doped coal tar pitch was con-