The study of 12 European countries commissioned by drugs giant revealed that 95 percent of adults believe a man's sexual confidence is the essential ingredient for a good sex life.
And 84 percent of men surveyed believe the most important element of a man's sexual confidence is his ability to please his partner sexually, while almost three quarters of women questioned agreed.
However, more than a third of women believe their partner would like to experience harder erections in order to improve their sex lives.
Spanish men were the most concerned about their erections, with 83 percent saying they would like to be harder in order to improve their sex lives, while Turkish men were second on 80 percent and Italians third on 76 percent.
German men are the most comfortable, with just 40 percent saying they wished they had harder erections.
"These survey results confirm previous research which shows that the hardness of a man's erection is intrinsically linked to confidence in his ability to please his partner sexually," said Dr John Dean, Sexual Physician at the independently owned non-profit London Clinic.
"Men need to feel confident about sex in order to enjoy their sexual experience, but to feel sexually confident, men also need to know that they can both satisfy their partner's sexual needs and get a hard erection."
The survey of 8,576 men and women also showed that 90 percent of respondents believe a lack of sexual confidence can have a negative impact on a man's overall self-confidence.
The findings confirmed that erection problems increase with age.
Ian Banks, a doctor and consultant for the independent British-based Men's Health Forum, said: "Erection problems can affect men of all ages and are more common than people realise. This survey shows that 70 percent of European men between the ages of 25 to 64 years are experiencing hard erections, this decreases to just one in two for men aged between 55 and 64.
"As a result, these men may be missing out on being sexually confident and the ability to please their partner, and are also at risk of depression, anxiety and low self-esteem."
Herewith the percentage of men who would like to experience harder erections in order to improve their sex life:
Spain: 83 percent
Turkey: 80 percent
Italy: 76 percent
Britain: 62 percent
France: 57 percent
Belgium: 50 percent
Sweden: 47 percent
Romania, Denmark: 46 percent
Netherlands: 42 percent
Finland: 41 percent
Germany: 40 percent