Colon cancer is the most commonly diagnosed gastrointestinal cancers in developed countries with varied incidence and the onset age of disease worldwide. Overall, 161 participants who were under patronage of a local relief foundation and referred to the endoscopy ward of Razi Hospital affiliated to the Guilan University of Medical Sciences. These patients have been aged more than 50 or more than 40 years with history of colorectal cancer in their first-degree family were enrolled from March 2016–March 2017. Demographic information were collected. Colonoscopy was performed and histopathological evaluation of observed lesions and polyps was done. Most of participants were female (113 individuals, 70.2%) and aged 50–60 years (83 individuals, 51.6%). Seventy-four (46%) had certain lesions. Most of colonoscopy findings were observed in the ascending colon in which depressed polyps and diverticulum were most frequent. However, rectum showed the most histological findings. All polyps of descending and ascending colons were neoplastic, while most of rectal polyps were non-neoplastic. Male patients, who were aged more than 60 years and smokers had significant higher percentage of both lesions and polyps in their colon (p<0.05). Moreover, significant positive association was detected between exposure to harmful industries and having polyps (p=0.01). We found male gender, higher age, smoking, and exposure to harmful industries as important risk factors for having colorectal lesions, which must be confirmed in further studies.