Frequency-wavelet domain deconvolution is applied to in vivo THz skin measurements to diagnose and asses treatments for skin conditions such as eczema and psoriasis. This method significantly enhances usable signal and improves the accuracy of the extracted impulse response function compared to conventional double-Gaussian (DG) deconvolution signal processing techniques. For example, the thickening of the stratum corneum (SC) layer of the epidermis common with psoriasis formed a trough in the impulse response function that was observed with the frequency-wavelet deconvolution technique, but was unobserved with conventional DG deconvolution.