The simplest definition organic farming is a production system, which excludes synthetic inputs and resorts to external inputs only where the system cannot be sustained by internal recycling. Recentstudies comparing conventional and organic farming have shown an increase in organic matter, nutrient content, and microbial biomass in organically managed soils. The present study was undertaken to evaluate how conventional and organic farming systems affected the yield and some quality properties of lettuce by investigating the effects of some natural substances (blood flour, manure, liquid seaweed extract etc.) on yield, quality and nutrient content of organically versusconventionally-grown lettuces. As a conclusion, results of both years showed that the conventional growing had higher yield than organic growing, respectively 20% in total yield and 21% in marketableyield. On the other hand there was no difference in terms of food nutrition value and quality and that is why it is possible to recommend organic lettuce growing as it has much more positive effects onhuman health