For a sample of size two from a continuous density f(x) with support on the positive half-line \((0,\infty )\) , the distributions of the sum of the two variables is usually of a different character from the distribution of the maximum of the two variables. It can be verified that, surprisingly, in the case in which the variables are half-normal, the distributions of the sum and of the maximum are of the same type. After discussing two alternative elementary proofs of this half-normal property, we show that, under mild regularity conditions, it only occurs if the two i.i.d. variables have a common half-normal distribution. The analogous case in which samples of size greater than 2 are involved is also discussed.