Distribution estimation for noisy data via density deconvolution is a notoriously difficult problem for typical noise distributions like Gaussian. We develop a density deconvolution estimator based on quadratic programming (QP) that can achieve better estimation than kernel density deconvolution methods. The QP approach appears to have a more favorable regularization tradeoff between oversmoothing vs. oscillation, especially at the tails of the distribution. An additional advantage is that it is straightforward to incorporate a number of common density constraints such as nonnegativity, integration-to-one, unimodality, tail convexity, tail monotonicity, and support constraints. We demonstrate that the QP approach has outstanding estimation performance relative to existing methods. Its performance is superior when only the universally applicable nonnegativity and integration-to-one constraints are incorporated, and incorporating additional common constraints when applicable (e.g., nonnegative support, unimodality, tail monotonicity or convexity, etc.) can further substantially improve the estimation.We consider the following statistical problem. Suppose a random variable (r.v.) X and its probability density function (pdf) f X (·), cumulative distribution function (cdf) F X (·), and various quantiles are of interest, but only a random sample of noisy observations {Y 1 , · · · , Y n } are available with which to estimate the pdf, cdf, and quantiles. The underlying model is Y i = X i +Z i , i ∈ {1, 2, · · · , n}, where the Z i 's represent observation errors and are independent of the X i 's. As is typical in the extensive literature on density estimation with noisy observations, (e.g., Carroll and Hall [1988], Stefanski [1990], Fan [1991], Diggle and Hall [1993], Delaigle and Gijbels [2004], Hall and Meister [2007], Meister [2009]), the pdf f Z of Z is assumed to be known. Existing estimators for this problem have slow convergence rates and poor finite-sample accuracy. Although their asymptotic convergence rates are optimal and thus cannot be improved, in this paper we propose new estimates based on quadratic programming whose finite-sample performance improves over existing estimators substantially. We note that most of the prior work on this topic casts the problem directly in terms of pdf estimation and refers to it as density deconvolution, recognizing that estimates of the cdf and the quantiles can be obtained in the obvious manner from an estimate of the pdf. We adopt the same convention in this paper, although we are interested in cdf and quantile estimation, in addition to pdf estimation.For the additive measurement error model, the pdf f Y of Y is the convolutionThis convolution in the spatial domain corresponds to multiplication φ Y (ω) = φ X (ω) · φ Z (ω) in the Fourier domain, where φ Y denotes the Fourier transform of f Y (likewise for φ Z and φ X ), and ω denotes frequency. In light of this, one classic and popular method is the Fourier-based kernel deconvolution (KD) (e.g., Carroll and Hall [1988], St...