We conducted a population-based cross-sectional epidemiologic survey of asthma and COPD in an adult representative national sample using information obtained from the Health Search Database owned by the Italian College of General Practitioners. General Practitioners who had a list of patient population of 909,638 individuals (429,962 men and 479,676 women; man/woman ratio [M/WR]: 0.89) ≥14 years old at the end of December 2009 were selected to be representatives of the whole Italian population. Cases of asthma and COPD were identified on the basis of the ICD-9 codes. The total sample included 55,500 (6.10% of the entire population; 5.49% of men and 6.64% of women; M/WR: 0.74) subjects suffering from asthma and 25,762 (2.83% of the entire population; 3.51% of men and 2.23% of women; M/WR: 1.41) subjects suffering from COPD. The asthma/COPD ratio in general population was 2.16. The odds ratio (OR) was chosen because asthma and COPD had a prevalence less than 10%. The OR of developing asthma decreased with age both in men and women, but in the first group of age (15–34 years) it was higher in men vs. women (1.69 vs. 1.00) although it became lower than 1 from 35 years old and up in men and from 75 years old and up in women. On the contrary, the OR of developing COPD became higher than 1 from 55 years old and up both in men and in women and progressively increased with age (in the group 75–84 years, it was 6.16 in men and 4.07 in women, respectively).