OBJECTIVE Brittleness and breakage of hair is a common complaint in the geographical area of Saudi Arabia where we work. This area has a high level of hardness in normal tap water. We aimed to study and compare structural differences and relative deposition of calcium and magnesium salts on the hair shaft surface using scanning electron microscopy (SEM) between hair shaft samples from normal, healthy volunteers treated with hard and soft water. METHODS Hair samples obtained from 20 healthy volunteers were divided into two groups. One group was treated with hard water for 3 weeks and the second with soft water for the same duration. SEM was used to assess hair shaft surface damages and relative deposition of calcium and magnesium on the surface of the hair. RESULTS There was no statistically significant difference between the study and control group as far as surface changes under SEM were concerned. As far as the relative deposition of calcium and magnesium was concerned, there was no statistically significant difference in calcium deposition between the control and study samples (P = 0.28). On the other hand, magnesium deposition showed a significant difference between both groups (P = 0.001), with a higher level in samples washed with hard water. CONCLUSIONS Hard water may be associated with increased deposits on the hair shaft surface, however, this does not necessarily translate into evident structural surface changes, as evidenced by SEM.