The principles behind up-conversion time correlated single photon counting (TCSPC) lidar are presented. This technique can easily extend the detection range of conventional SPADs to reach into the MIR by utilising nonlinear processes to up-convert the wavelength of the MIR to the visible or NIR. The up-converted light can then be detected by a standard Si-SPAD. This allows for high resolution and sensitivity to be achieved while operating the system at room temperature. The technique is demonstrated through a short-range lidar system measuring off diffusely reflecting targets. The system was operating at 3 µm with pulse energies around 3 nJ and a pulse width of 300 fs. The up-conversion was performed inside a PPRKTP crystal placed within a Nd:YVO4 laser cavity operating at 1064 nm, which generated pulses at 790 nm. The temporal FWHM of the lidar response was 76 ps, and the system showed sub-mm range accuracy, demonstrated by scanning 3D targets.