In the present paper mortars with air lime and hydraulic binders (natural pozzolan and white cement) were manufactured using standard sand and different water-binder ratios (w/b). The influence of the w/b ratio on the open porosity and pore size distribution as well as on compressive strength at the age of three months was recorded. It seems that the pores that were mainly affected by high w/b ratio were different in different binding systems. In air lime mortars, pores with diameter larger than 500μm and those of 1-100μm are affected while in mortars with hydraulic binders pores of 100-500μm and 0.1-100μm are affected. Micro pores with diameter less than 0.1μm seem to be unaffected in all binding systems tested. In air lime mortars, strength decrease was not proportional to the increase of w/b ratio. On the contrary, in mortars with hydraulic binders both strength and porosity are changing proportionally to w/b variations.