A diesel particulate filter (DPF) is used to remove particulate matter (PM) from the effluent of a diesel engine. A major technological challenge in the operation of the ceramic cordierite filter is to prevent formation of local high temperatures that can melt the DPF or generate a thermal stress that may cause cracking. Most previous studies of the temperature rise during the DPF periodic regeneration (combustion of the deposited PM) considered cases in which the inlet velocity to all the parallel channels was uniform. A wide-angled cone (diffuser) is sometimes used to connect the diesel engine exhaust pipe to the DPF leading to a nonuniform velocity to the inlet channels, with the highest attained at the DPF center. We used a PM deposition and regeneration computational model to investigate the impact of the inlet cone on the DPF behavior under stationary feed conditions. The cone led to mal-distribution of the deposited PM, with the highest thickness in the DPF center. The highest regeneration temperature when using an inlet cone may be quite higher than when it is absent. Moreover, the inlet cone can generate higher temperature gradients and the resulting thermal stresses may crack the ceramic support. The largest radial thermal gradients are encountered close to the wall in the downstream section of DPF, shortly after the temperature inside the filter reaches its peak. The cone leads to a slightly faster regeneration than when it is not used.